With 12.1 dropping yesterday I have multiple BIG-IPs I need to upgrade in my lab environment. In the lab we have a CIFS share that stores the ISOs so I can upload the 12.1 ISO to each F5 from that filer with the following command.
mkdir /tmp/iso mount -t cifs -o username=user,password=user //10.1.1.254/ISO /tmp/iso/ rsync --progress -a /tmp/iso/F5/12/BIGIP-126.96.36.199.0.1434.iso /shared/images/
You could also remove the BIGIP-188.8.131.52.0.1434.iso on the rsync command and it would copy all ISOs to the BIG-IP. This could easily be added to a crontab to make your life easier.