I attribute the drastic change in patterns to conversion from juvenile to adult markings. Kinda like how birds tend to look drastically different between juvenile and adult plumage patterns.
as for the wings, the bottom side have peacock spots. in the case of all the spots, they're more likely rings that I didn't finish drawing. that applies in the case of the seeming bullseye patterns almost all over his body. the fins, the wing 'bullseyes' on the top side. so on. the peacock spots are, predictably, two-toned on the character. the crescent part is usually a much richer, darker shade of blue, with the other part being lighter. the long feather-like patterns would be filled out, and would glow a bright whitish blue [again, think Tron]. hence why I state in the RPG that it's startling and used as a defence mechanism. imagine sneaking up on him at night while he's curled up, looking small. suddenly he turns on you and rears up on his hind legs [making him, previously, the height of a two storey house. now 3 stories due to the size boost], and unfurling his wings. you get this enormous wall of light right in front of you [Septimus has enormous wings, as you probably noticed by looking at the new pic

. his wingspan is huge. 90+ feet]. suddenly, he doesn't look so small and vulnerable

Also, yes, his wings in the new image aren't torn up like the old one. in the previous, he tended not to put too much effort into keeping them intact, because A) it intimidated enemies to see rips in the wings. made him look like a hardened fighter, and B) It would waste too much of his energy, that he could make much better use of elsewhere.
But since Thurduunax [Who I will soon be posting in image of] went to the effort to basically fix all Septimus' growth and energy problems, he patched up the wings while he was at it. hence the wings being intact.

Notice that the line running across Septimus' eye isn't a scar. it's part of his Clan Symbol [shown next to the head of old Seppy for a clear view]. It's stretched with his face, and the dark portion of the tear-drop shape on his nose as been stretched over his nose horn. hence why it's black in the picture.