Found this photo online, and realised that the non-iSight iMac G5s were the first iMacs to have VESA mounting support, but more strangely, the iSight iMac G5s lost VESA support again. These old VESA mount adapters can still be found on Ebay (not my listing):
I think a Vesa mounted iMac G5, especially with bluetooth keyboard + mouse, could be quite a nice display piece / digital art frame!
I think a Vesa mounted iMac G5, especially with bluetooth keyboard + mouse, could be quite a nice display piece / digital art frame!