Wanted to make a list of Blast Mode Digimon that appeared in Accel. I don't know if I want to include the "X-Antibody Blast Mode" Digimon, as some of them don't have that much differences (unless someone points them out):
Ultimate/Perfect Digimon
Mega/Ultimate Digimon
IMO Rosemon Blast Mode's design should've been reused for Burst Mode, it would've had a design that stands out like the other three burst digimon rather than simply being a recolor.
And to compare, here're links to the regular sprites in Accel. I'll try to explain how I think the Blast Modes differ as best I can.
Andiramon The middle horn grows longer, the ears have bands on them, and I think cracks (or stripes?) are spreading from the jewel in the center of its chest. Cracks/stripes also appear on the knees of its pants. Not sure what the hell's going on with the arms, but I think each arm is splitting in two, with the left arm also twisting back together. The elbows grow protruding spikes, as well.
Yatagaramon It forms a chest plate, which is either strapped to it by a harness, or I'm looking at the side of its wing which grew some kind of armored edge. Either spikes or raised feathers now protrude along the top of its head down along its back.
Dagomon Its left arm forms into an axe. That's pretty much it.
Gerbemon It foregoes its shield in favor of dual-wielding bazookas.
Hippogriffomon Forearms grow bulkier, and I think it grows an elbow spike. Wingspan's extended.
Chimairamon I'd have to look at this sprite animated to get a clearer picture, but I guess it now has a perpetual fireball forming in its mouth (which I guess isn't too out there considering the Burst Modes have perpetual aura-like features, albeit ones that aren't requiring their mouths to constantly be open).
LoaderLeomon The length of the mane extends outwards.
Mamemon Left fist grows in size and it gains spikes (likely the bolts normally on the glove turning sharp). Mouth opens wider and the eyes turn darker while taking on a more sinister look.
MarinDevimon Hands grow bigger and the emblem on the back of them take on a darker tone. Eyes slant more horizontally. Probably grows an extra set of tentacles.
Matadrmon The sleeves and the swords on its hands extend (actually, I wonder if the Blast Mode is what's being depicted in the profile art, while its vanilla form has significantly shorter swords). The glasses(?) extend and gain some upper protrusions, and its wings (which are depicted in its profile art as being MUCH smaller than the sprites for both forms) gain some darkened edges.
MetallifeKuwagamon I really have no idea. Its hands turn into giant crab pinchers?
Scorpiomon One of the blades on its left claw extends and its tail stinger grows in size. Eyes grow larger, and the horns on the sides of its head grow longer.
Tankdramon The rifle barrels grow bigger. Grows a horn on its head.
Volcdramon The volcanic vents along its back form into one giant vent.
Whamon Grows a horn, likely to resemble a narwhal. Pectoral fins grow larger.
BanchoLeomon The sleeves and coattails of its GAKU-RAN stand upwards. The sprite's no longer holding its sword (whether it's merely sheathed or gotten rid of completely is unknown, but the implication seems to be that the Blast Mode fights exclusively with its fists). I don't think expression changes in the sprites are of particular note (since they're most likely not a constant), but just so nobody brings it up, this particular sprite depicts BanchoLeomon with an open-mouth smile. Incidentally, Blast Mode looks nothing like the Burst Mode depicted in the anime (in which BanchoLeomon takes on a fiery aura and its mane spikes upward in a Super Saiyan-like fashion).
Chaosmon The horn on its forehead extends outwards, and the sides of its head grow longer. Other than that, it's kinda difficult to tell what changed because the vanilla form's sprite isn't especially accurate to the profile art (for instance, both sprites show it with pectoral muscles as opposed to just a white cloth surrounding a spherical core). I guess the pecs grow more defined (which could suggest the white cloth becoming more solidified, maybe?), and the Darkdramon arm becomes shorter and more stout, while the BanchoLeomon arm's mane grows more jagged. It also grows shin guards.
Mugendramon A cannon extends out of its mouth (much like Chimairamon, its mouth might be constantly remaining open, which seems fitting given how those two Digimon are related). Also, the side of its left shoulder becomes darker (this might just be the sprite trying to depict it at more of an angle, though).
MarinAngemon Now this is an especially interesting Blast Mode. Despite being stated to be an Angemon species in name only, MarinAngemon's Blast Mode seemingly gives it a fallen angel form. It trades its angel wings for bat-like devil wings, its eyes become more narrow and possibly darkened, and it gains some kind of mark (possibly a jewel) on the center of its forehead.
Mercurymon The mouth of the wolf mask closes, hiding the humanistic mouth underneath (or perhaps the wolf's mouth now becomes Mercurymon's mouth?). The hairs of the mane (or possibly just the top portion of the mane) spike backwards. Other than that, the sprite now depicts the knife, Aztec, being held at more of a diagonal angle (whether or not this implies any changes being made to Aztec is unknown).
MetalEtemon Just kinda has all of his hairs standing upwards (which is awkward, since Etemon and its evolutions are supposed to just be wearing a monkey suit..... which has now been metalized in the case of MetalEtemon..... and therefor doesn't have any actual hairs, but nevertheless, the Blast Mode sprite gives that impression).
Rosemon Grows leaves and/or differently-colored petals which extend out the back of its head. The rose on top of its head seems to have opened up and now displays a visible stigma. I don't know what's happening behind its legs, but my guesses would be either that the cape grew longer and gained more protrusions along its side (though this would just make it be more in line with the profile art than the vanilla sprite's cape), or its hair grew longer and became untied.
Spinomon Grows a large horn on its forehead. Either its eyes or its eyebrows grow larger. It gains a protruding fang along the side of its mouth. The crest along the back of its head gains a darkened edge. The swords along its back grow longer. And both its hands and its feet grow bulkier.