Scratch

Ok, so if you're looking to use a character that actual moves around and interacts with other characters then there are many different combinations. Just remember you have an
upload limit of 10,000 kb, so don't make and infinite number of sprites.

I would suggest having a character who can choose between the enemy or allies (most likely medieval) and each side will give the character tasks against the other side. However, what would be interesting is having the ability to lose.

The character could upgrade his weapons and armor and whatever else.

Have you considered drawing up and scripting some generic "dialog sprites"?
Many people, myself included, have a use for a large sprite (200x200) which looks nice, scales well, and could fit into sci-fi/fantasy/rpg frameworks as a villain/hero/etc. The scripting is pretty easy (indexed lists for dialog, visibility (true/false so the sprite will hide), dialog type (think or say), and duration in sec) and then a simple loop which would use a single numeric variable with a repeat to go through those lists and display text the sprite would say. The sprites could be exported with a bare-bones script which would make it easy for others to incorporate into their projects. And if you make them generic and stylish, and even uncolored, then Scratchers would be able to finish them up and make them unique. I wrote up a dialog testing script that I can upload if my description seems cryptic. It uses silhouettes because I wanted to focus on the scripting rather than failing at the art first and then rage-quitting the whole idea. 

How about:
You have a small ball. If you throw it on a red spot a red portal appears. If you throw it on a blue spot a blue portal appears. You also have Portal Paint to make these spots.
If you get in one you come out the other. You can't use portal paint or the ball in some places.

Lets have a stickmania rpg! you can do anything exept innapropiatness and powerplaying and not being a stickman.:-D:-D:-D:-D:-D:-D:-D::-D