Hi!
Some time ago I've made a design kit for Adobe Photoshop which helps with game cards design. It's prepared for printing, but can be used also on digital media.
I've attached my concepts done with this design kit (they're also included in the file itself as examples).
This details and the design kit are available here.
I hope it'll be useful for someone :)
Do you mean automatic creation of a large number of cards based on some text file? This design kit is a Adobe Photoshop graphic file and set of layer styles, so you have to create each individual card. Of course if you create a design for a card you can add text for each of them as a separate text layer to export them individually.
It's possible to automate the process but it involves creating a custom script using Photoshop API (available in 3 languages, e.g. JavaScript) to put the texts from an external file. API documentation for Photoshop CS6 is available here.
Size of cards is set to dimensions described in the item details page, but of course it's possible to change them. If you only want to resize the cards keeping the aspect ratio you can prepare them in original size and then resize the whole file. You can also resize the file before designing and then add text and other stuff. In this case some layer style scaling (one of Photoshop options) could be helpful. If you want to create a card of different size and aspect ratio yo have to do some more work with background layers and layouts - it's not hard, but some knowledge of Photoshop would be helpful.
The file itself is prepared for a design of individual cards. When you have your cards designed you can export them e.g. as JPEG or TIFF images and prepare a large file for print of multiple cards. I didn't prepared multi-card file due to PSD file size and performance reasons (large number of cards with several styled layers could be a hard stuff for some machines - rasterized and flattened final JPEGs or TIFFs are better in such cases). Another problem is the paper format - each person may want another size (different for US or European ISO standards) so it's hard to fit everyone's needs.