I went to the brink page on facebook and then saved one of the photos to my computer, cropped it and then set it as the avatar on this account. I was wondering if that is not allowed or if it's ok to do.

As long as it's not copyrighted then it's allowed.

You'll be fine

You should be fine.

The cyber-police are gunna get ya they know where you are and are on their way .. you have been warned.
...
Just kiddin, that was a reference to Jessie Slaughter's dad, a bunch of trolls basically bullied Jessie Slaughter and her father said to the trolls that they 'dun goofed' and the 'cyberpolice' are after them

From the forum rules:

Guidelines

• Avatar images will be resized by the forum software to a maximum of 90 x 120 pixels and 100KB file size. It is best to find an avatar that falls roughly within these limits or they may look distorted or squashed.
  
  
• Please do not use Bethesda or associated companies logos, or moderator logos as an avatar as it is misleading to other forum members. Doing so will result in it being removed.
  
  
• Please do not use an avatar already being used by an Admin or moderator as it is misleading. Again it will be removed.
  
  
• Your avatar cannot contain any advlt rated or inappropriate content. We also remove avatars that are lewd, overly sixual in nature and/or graphically violent. If it contravenes any of the forum rules then it will not be allowed and the moderators have full authority to make decisions about the suitability. If you are in doubt, contact a moderator via PM to check.
  
  
• The only file types accepted are .gif, .jpg, .jpeg, .png
  
  
• Animated avatars will need to be resized to 90 x 120px before downloading onto the forum otherwise they will not work.
  
  
• Animated avatars that could induce epileptic seizures are prohibited. These include simulated strobe flashes or negative/positive reversals, fields of bright red, illusions of continuous motion in black and white or bright colors, and flashing at a frequency of 4 Hz (4 strongly contrasting changes per second) or greater. Again, if you are in doubt a PM to a moderator first is advisable.

It will be OK.

Case closed.