Alrighty then, I have finished a sheet for the backs for Gen 4. Here's a direct link to a photobucket album with all four sheets.
As far as the front sprites go, feel free to use any of the following
Made by WesleyFG
From your 493 project:
Since I only resized front sprites when absolutely necessary these should all fit in with your resizing scheme. Unfortunately that breaks down a little with Arceus since it doesn't really fill the canvas well. I think a custom sprite might be better there, but I'm by no means capable of that. Obviously credit Wesley if you decide to use his sprites, and as I've already gotten permission from him to repackage them you should be fine there as well.