Uploading photos to a facebook fan page is just 5 easy steps. It is similar to uploading photos on your own page / wall.
Step 1: Go to the fan page your want to post on and look for the box up top where you would type in a message:
Step 2: Click Photo (right next to status), then Click Upload a Photo.
Step 3: Click the Choose file button.
Step 4: Find the file (Photo) you want to upload and then click open.
Step 5: Type a description for your photo in the box and click the Share button to post.