Those enemies from Darius Force are really cool too! Definitely might be good for some inspiration.
I got the idea for the Laser Snail from an artist I follow on twitter, that was trying to get a lasersnail hashtag trending. When I was drawing it I was kind of thinking about a potential Metal Slug enemy, kind of like the giant crab boss from MS3.
Also here are some more drawings I did late last year. I was practicing a lot with my newly acquired markers at the time. The High Priest and the Black Market Arms Dealer are also accented with metallic paints, but it's hard to tell in the pics.
Yeah, it wasn't until afterwards that I saw the correlation with Captain America's shield. In hindsight I should've just done a typical pentagram instead. I could probably alter it a bit by adding some more detail to the empty space in the circle as well as the star.
Been doing a bunch of 1-bit pixel art lately, between my last game Maze: The Ritual, and my current game project. A lot of it lately has been mostly monster sprites. Though I decided to take a break from game-related stuff and just did a personal piece last night for fun. Hope you enjoy!