Hello again! Thank you again for your advice! I admit I did not follow it to a T, but I did put together a more thought-out palette to use and I've reskinned just about everything to match. Regardless of color, I added a border to the enemies so they can be more easily seen in just about any palette. None of the textures are set in stone, but I think even just having an intentional color palette makes it look much better!
I also did a bit of tweaking to enemy spawning, I tweaked enemy movement, and I added a few small features.
Just wanted to let you know I really appreciated your comments!