Yup, that's the case for most forums. What I do is make the icon in photoshop, save it as a .JPG file and upload it to tinypic.com. Once it's done uploading the picture, the site will give you multiple codes, one of them being a URL. The URL is best for the forum avatar and signature. If you just wanted a picture in a post, you just put [IMG] before and after the URL. I suppose I could have done this as a guide but it's really short.