I have collected my Star Trek designs into their own sub-gallery, and want to thank everyone who has watched and commented on this process. Am I finished? Never. I have plans to add a sketch to each background and I'm rethinking the colors...but I get ahead of myself. This has been an interesting exercise - to modify established designs into my own, evolving style, while not straying too far from the original. Successful? Maybe - I do like that they all seem to exist in the same world. One isn't too realistic, while another more cartoony, etc.
One big trick I learned is to give each character a specific and obvious design "thing." The spiral of the Ferengi's ears, the serrations on the Mugato's horn, the mortor-board head on Spock - a design element that sticks out, defines the character, and will help you to easily identify that character in the future. Usually this can be done with a character's hair-do. Silhouette Disney's Ariel and Belle, bald, and they look similar enough. But their distinctive hair will always define them. Live-action actresses sometimes go to great lengths for a unique and defining hair-do. A well done design "thing" will keep you remembering that character, and hopefully become as ubiquitous as one of their catch-phrases...
Live long and prosper...
...and thanks for all the comments!