You can't easily put photos on an iPad from more than one computer. However, you can email photos to yourself from various computers and download these photos to your iPad.
Tú kanst ikki lættliga flyta myndir frá fleiri enn eini teldu á ein ipad. Tó kanst tú senda myndir til tín sjálvs frá ymiskum teldum og taka hesar myndir niður á tín ipad.