I don't know how to professionally, digitally enhance my work yet but I played around with the exposure, contrast, and saturation. Here's my first Deviant Art upload. Some of my favorite childhood robots/cyborgs/mobilesuits.
I know the first three!!!!!
Very well done. I don' think it needs much enhancements other than what you mentioned.
Thanks for the feedback. I was thinking of maybe adding a unique background for each.
I used Blick Studio Markers, Manga Pitt Artist Pens, and Prismacolor Colored Pencils on Bristol Paper.