Filesharing: set up an account at some fileshare site, there's enough out there.
Theme: can be important, but a consistent overall look is better.
Here's a thought: pick a single front "framework" to use on ALL the cards. For example, a white border (or black, or whatever color) around all the front designs for total edge consistency, and identical index styles on all the cards. Have ONE PERSON design the indices for ALL the cards, using consistent placement throughout.
Let whoever's doing the back choose a good front border that's consistent with the back artwork/border.
I have that sample deck from USPC's Custom division - not an easy thing to look at in a squeezed hand, I tell you.