DougJustDoug: Vulcan Derg looks fantastic and I really like the furnace motif, though something seems a bit missing from the head area. I was wondering about the idea of giving it a horned helmet but that's a Viking stereotype, so maybe something more like a Roman horsehair helmet but with the plume being made of flames could work? I really like the furnace markings on the underbelly, though, and I look forward to seeing it in color.
Slapperfish: Your "glassilisk" has improved steadily with each redesign, and I like how it looks like it's swimming in the lava - not many burrowing Pokemon are only partly exposed a la Diglett! The bubbles could do with being a bit less in number though to make it easier to sprite or 3D-texture, maybe just like five or six around the throat area for example to retain the lattice-like look. Perhaps given the dorsal fins you could even give it a longer body that rises in humps like a sea serpent from the surface of the lava?
Pipotchi: The best entries among yours for my taste are the cowboy lizard for the sake of personality and the Welsh dragon because of how majestic it looks all in all. I suggested on Discord to give it a knight-like motif and I'm glad to see it being pushed here, though maybe making the entire body segmented and armor plated like Rhydon would help with that angle (and make some parts like the tail look less plain). A pair of horns wouldn't be a bad idea, either, maybe even coming out of a brow ridge shaped like a knight's helmet visor. The flag-wings are an excellent idea though and maybe adding a few flame-like patterns on them for visual interest could help sell the Fire-typing better than just the flaming head plume.
A_Magical_Liopleurodon: The kirin with a lamp on its head looks equally majestic and silly and I love it! I don't know how it fits Regenerator but if you can find a justification for it I'd recommend following through with it. As for the gorgon, it feels a bit weaker to me even though it
would fit the ability better, partly because it's a bit hard for me to make out what's what. Making the upper arms thicker rather than just black strings would be good, and instead of flaming spikes, what if the tentacles had flames on the ends resembling snake heads? The segmented look is pretty cool, though, with an almost worm-like feel to it - maybe have glowing sections in between the segments as though there's fire burning within.
Quanyails: Both of your ideas look lovely, but the chef's oven gecko dragon is my favorite purely for the character factor. I think it could still fit Regenerator because of how many geckos can regrow their tails, so maybe include that in your design a little more clearly - the tail does look cut-off to invoke a chimney, but perhaps the smoke could be shaped more like the rest of the tail like a phantom appendage. A few extra scales here and there on the upper arms and the tangible part of the tail could also make it look less plain. Great work all in all, though! As for the firework axolotl, I like the design, but the color scheme is a tad clashy - I get that it's supposed to be bright, but maybe have the showy colors restricted to the front, and make the back half a more desaturated pale grayish blue like a smoke trail. The magical girl aspects are hilarious and awesome, though - I can easily imagine this thing doing all kinds of crazy poses in battle!
StephXPM: Nice work with that comet dragon! It'd be interesting to see it in action, though given that it's supposed to invoke a meteor, maybe a pair of wings would be nice, like how Chinese dragons grow wings in the last stage of their life cycle. You could even have them be a part of the mane and flowing towards the back like comet trails. Hopefully we'll get to see a finalized artwork soon with a more action-packed posture, but for now I'd love to see where this design goes and how you'll change up the small details to make it truly special.
Magistrum: Lizard superhero is a precious boi! I like how you justified the flame elements of the frill, but I was wondering if you could make it more like bright orange, red, and yellow like flames rather than the darker red there - it could easily come off as Fighting/Dragon rather than Fire/Dragon. A few more details hinting at the Fire typing can't hurt, either - what if the tip of the tail also had a flame-colored flap of skin (not an actual flame like Charizard though) suggesting a sparkler or even a speeding flame trail? I'd also suggest adding skin flaps on the arms or on the back as well resembling a cape, though I don't know if that'd be too extravagant given that the massive frill already suggests that.
Sunfished: Bird dragons don't get enough love, and I like that you've exploited the peacock's tail by making it look like an explosion. I don't see as much of a Dragon typing as I do Fire, though - I know I shouldn't question this given Altaria, but why is it part Dragon? There are a few Japanese dragons with bird-like bodies rather than serpentine ones but keeping the signature Asian dragon heads, so I'd suggest giving it a more draconic head with a reptilian snout with teeth instead of a beak like prehistoric birds and bird relatives, a scaly head and neck
a la Archeops, and possibly a pair of horns or antlers instead of a feathery crest (or possibly alongside that? I'm not sure).