I believe that you can upload local files to the wiki, then link to them. Then png files should work.OK spent last night wrangling with GCS since that's what it seems you're looking for, and I got a dwarven cleric done!
Now, I can output it to a .gcs or .pdf file or take screenshots of it to get a image, but if I'm deciphering my forum tool bars right then I don't think I can upload local files and can only link to web images. Can I send you the .gcs file somehow, or should I just type it up in plain text for you to punch it in to GCS yourself?
Can you find the instructions for uploading images on the wiki?