This...this is awful.
Woo, where to begin...
First and foremost, I like the idea. A lot. But, like many Flash games, the execution is terrible.
First of all, give us more options. A selection of colors not unlike Balloon Duel (search for it if you've never played it) would be nice. Also, make the creation tiles smaller, while still covering the space the present tiles cover. That way, there's more space for creating creatures. Some pre-made monsters would also be great.
As for the actual gameplay, it's atrocious. Basically. it's boring, daft interface in which you haphazardly select from a list of redundant "stats," then watch as your circumsized Mega Man head attacks another poorly drawn character with, get this, ARROWS. There is literally no variety in the attacks your character can choose from. None.
The system that determines which character attacks first makes little to no sense. I can easily see that whoever has the higher number each turn attacks first, but how are those numbers accumulated? What do those attriibutes (power, speed, agility etc.) even DO? In my experience, they don't seem to affect the battle in the slightest bit.
Maybe I'm just a dumb 15-year-old, but you should try to make a fun, smoothly paced battle system that people can actually comprehend. Still, I wouldn't stray from this idea. Just make a funner battle system and give us more creation options, and you're all set.