My exam's over and I'm here with updated information.
I am thinking the Flash size should be about 800 px in length, maximum. Which makes 600 in width. So the canvas size would be a little less than that, say, 720 x 540?
Images are varied, themes are varied, but I'm thinking of keeping it T-rated at the most, to fit in with players of the series (nearly the entire series has been T-rated except for Brawl Royale). Any style is welcome -- but again, I would not like too much character art. Equal focus has to be given on the characters, the atmosphere, the little things in EBF, Adventure Story and Bullet Heaven, the enemies, the weapons etc. If you're even inspired by the music, you're welcome to make something out of it!
To this day I haven't found a person who'd gladly put together the Flash. I'm not sure if Matt is up for it, but technically speaking, he wouldn't be, since this is a tribute, and not really part of the canon series. Still, if he'd like to give input, I'll gladly welcome him.
On that note, this is the status of the collab over at the Audio Portal, so it has gained quite a bit of momentum there. And so far two artists have shown interest.
I'll be glad to do something on my own too, in terms of visual art (I've already got a project coming up for the audio). It might not be the best, but I'll try.