Appending letters (not numbers)

I'm looking for some help appending sequential letters (fileA, fileB, fileC, etc..) to the end of files. Appending numbers seems pretty straight forward using a number of systems, but I haven't found a way to add letters. Any thoughts?

For bonus, the actual feat I'm trying to accomplish is grabbing a number of images, automatically adjusting contrast, file size and adding borders, then renaming them based upon input text and auto date with a letter appended sequentially. So I'd start with Image1, Image2, Image3 and end with Name20160111a, Name20160111b, Name20160111c..." I've kind of got a workflow by using a single program to batch process the editing, then dumping the edited images into a folder that renames them, but I just can't get the letters appending.

Anyway, thanks for a partial or full, more elegant solution....

Thanks!

Right now you need to write a script to do that. There is an entry in the feature database for it already so I will consider it for future versions though.

Bummer. Thanks for looking at it. Does anyone have any other suggestions for work arounds?

J