What you are describing is a number padding issue.....
All you need to do is the following:
If you want to have more padding so to be able to render out more then 10000 then increade the "#" in the filename before rendering....
EXAMPLE: Face00001.tga is represented like "Face[#####].tga
So to increase the padding:
EXAMPLE: Face00000001.tga will be "Face[########].tga.....
Good luck!