How do I change my profile picture in the forums?

Oh. I can't explain why.
If I remember, we had to choose a category when uploading the photo ( safe for children, sexually suggestive etc ) Maybe you choose a suggestive pic ?
Also, make sure you used the same email address on the gravatar website and here.
I have no clue for other reasons leading to your profile picture not appearing here, sorry.

@zeropol this is a really late reply but I made an account and uploaded a pic on gravatar but it's been 3 days and it's not showing up on this website

Create an account here
Then, you'll can upload an image and crop it with the gravatar website tool.
You need to associate your account with the same address email you used here, or it wont work.
You may need to wait several minutes for your picture to be visible on SR2 website.
Hope it help !