It's a function of time and # of posts, but the exact thresholds aren't publicized so that would-be spammers can't game the system, so to speak. Just participate on the forums normally and it'll happen soon enough.
You're too new. You need to participate in the forums for a while, then the system will grant you access.
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The Dimension limits for this filetype are 80 x 80. We were unable to resize your file so you will need to do so manually and upload it again. Your file is currently 141 x 170.
The Avatar image doesn't meet the required specs! And I can't seem to reduce it's size with 3D Paint! Thoughts?