I recently created a set of rethemed cards for Dominion and Dominion: Intriguehere and here. People have started asking questions about image files suitable for printing, but I've never done that before. Any tips?
The cards were made with Powerpoint, and I made the images with screencapture. Is that sufficient? What DPI should I use?
Most universal file format would be PDF. There are free virtual printer drivers to create PDF files that do the trick, but some of those create hideously large files and have limited options to set desired resolution. (You could do that in Open Office, but downloading and installing Open Office just for this seem a bit silly.) There may be an issue with the card artwork, however. I'm assuming that you didn't draw it yourself. In that case, the artwork is most likely copyrighted and you would not be allowed to upload files using that artwork anyway.