I believe that will be left very much in Dougs hands. You can always look back through the Prevo Artwork threads and see the artwork submitted for those designs. Gen 4 CaPs will obviously have a lot less variety in terms of the looks of the designs compared to the array of designs in the Gen 5 Prevos.
I believe they will stick with sprites for the time being. There were discussions about Models (and I believe there were some artworks submitted as 3D models for CaP Proper) but I think the outcome was that Modelling was too advanced/complex for the majority of people for it to be feasible (bearing in mind there are 2/3 year courses at Universities for Modelling programs and the like).
Please read this thread: http://www.smogon.com/forums/threads/mega-evolution.3495506/ There is a firm decision to not create Mega's for involvement in CaP.
The Pokemon is implemented on Pokemon Showdown and playable on the CAP format.
I am not sure on the former, but the latter will most likely still be banned.
No. CaP/Smogon do not entertain these creations. CaP Pokemon are always made with community input (even the quick caps) and follow a structured creation process. You could try making your own Smeargle's Studio thread, they allow all sorts of artwork down there. Make sure you read the rules first though! The mods of Smeargle's Studio are pretty cool guys so ask them any questions you might have!
Hey, welcome to Smogon and CAP! I'd start by reading the CAP Newcomer's Guide and trying to catch up with the current project. Right now, we're in the middle of making a Pokemon whose purpose is to serve in a core with Lucario and Latias, and we're currently on the Art step. Currently we've decided the Concept, Threats, Typing, two Abilities, and Stats, which can be found by opening up just about any CAP thread and reading the first post. After we decide the Art we'll be working on the Name and Movepool, and you're welcome to participate in those discussions (as well as vote in the ongoing Art Poll).
Creating a Pokemon based off of artwork is certainly one method, and there are many projects around the internet that focus on making Pokemon around a non-competitive theme or design. However, the goals of the Create-A-Pokemon Project are to design Pokemon in order to learn about the competitive Pokemon metagame. While we make artwork, sprites and all that jazz in order to make our Pokemon believable (and because everyone likes that stuff), the competitive side of things is always more important here. As such, when deciding what we want to have our Pokemon do, as a concept, we look at the competitive metagame.
I do not believe they have been ruled out entirely... But for the time being do not hold your breath about Mega's ever appearing for any of the CaPs.
