One thing I have to try to take more care with on thumbnails is to realize how a lot of the color mixing will play out.
When designing the security team, I tried to give them a complimentary palette - purple/red/orange, further contrasting against Nova's sandy fur earlier - but it had an unintentional effect of Abigail's holo-hand blending in a bit with the orange environment.
I tend to save a lot of the palette planning for when I actually start to reach new environments, since colors are going to be picked digitally... but it can ultimately end up requiring a bit of improvising to ensure stuff doesn't blend together too much.