Third party apps, such as GoodReader and PrintCentral, will allow you to wirelessly transfer files - photos too, of course - directly from your PC to the iPad. You can open them there from the iPad's native Photo app.
Or, if you have the photos on a memory card (SD Card) then Apple sell a special card adaptor that plugs into the socket on the bottom of the iPad. You can simply plug the SD card into the adaptor and load them directly into the photo app on the iPad.
Tim
Scotland