Posting an image in a message body and putting an "avatar" are too entirely different things. I am at work right now but I can help you more tonight when I get home if you are willing to wait. I will write you a step by step guide. First thing that may be of some help is the images file size. To post an image in a message's body, it must have less than 100Kb. To use the same image as an avatar, it file size must be reduced farther still, below 32 Kb.
Picture's file size is dependent on 2 major things-
1. The images overall number of dots. An image that has 800X600 dots, has an actual number of 480,000 pixels that represent a certain color. The more dots a picture has, the larger its file size will be. So the same image reduced to 640X480 will have less dots and a smaller file size.
2. Image Content & Compression - A jpeg image use's compression to store all the data that represents which color a specific pixel will show. If you posted an image that was all completly white, the file basically says to the computer "display white for every pixel". An image with two colors, the file tells the computer place white in pixels 1-500, place black in pixels 500-800, etc. The level of compression you use changes the threshold where the computer sees different colors. So no compression at all, each individual pixel stores its unique color, with high compression many colors that are similar may be changed to one value, so that the computer can only store one piece of data that will represent many pixels in the image to reduce file size. While this reduction in data reduces file size, it also reduces the quality of the image as seen to the human eye.
Basically first reduce an images number of dots using photo software. Most monitors use a resolution of 1024X768. So if you reduce your image to less than that it will all fit on the screen at one time, and the person viewing it wont have to pan to see the entire image. I usually reduce it to 800X600 or 640X480. FOR AN AVATAR, you will need even smaller, try 100X100.
Then apply compression until the file size is small enough, or continue applying it to reduce the file size even more. This will let the image load over the internet faster, just don't go so far that the image turns unpleasurable to view it.
