Whoa! An amazing battle system AND a curious storyline! The combo moves and Brink Mode are especially interesting, can see many possibilities there...
You might have changed them by now, but two things irked me in the demo. One, the player can be pushed around by the last trainer when he walks around; and two, when selecting which Pokemon to use an attack on, the camera doesn't move to your ally. That confused me when both the enemy and I had Combees.
As far as graphics go, the vectors need work and they clash with the sprites. However, where most people want you to stick with the sprites, I have the opposite view. If improved, using vector graphics for everything could look amazing, and make Evoas really stand out amongst the myriad of fangames using sprites. The downsides are it'd probably take even more effort than sprites, and depending on how you've got animations set up, it might be more complex. Don't know how much it would affect file size, either. Anyway, just an idea.
If you are still looking for help with the graphics, I'd be interested in assisting. I'm a fairly competent spriter (although I haven't touched a Pokemon style in ages), Flash is one of my go-tos for drawing, and I've studied animation (mostly with Flash) for a year. PM me if you'd like some examples.
Anyways, I'll watch Evoas's progress. You've really got something cool here! :D