How to Change the Group Photos on Facebook
If you created a Facebook group or have been made admin of another user's group, you have permission to change photos that you and others have uploaded to the group's Wall. The only way to physically change a photo is to delete, edit and upload again. You can, however, change descriptions, add or remove tags or delete photos altogether.
Log in to Facebook.com and go to your Facebook group page.
Click the "Photos" tab.
Click a photo to open it.
Click the "Edit this description" icon (pencil) to alter the caption and click "Save" when you've finished editing.
Click "Remove this photo," then "Confirm," to delete the photo from the group.
Click "Tag this photo" and click on a face or feature to start tagging. Type the name of the person or object, or select a name from the drop-down menu, to tag. Click "Finished tagging" to end the task.