It will depend on the size of the photos and what else is on the iPad. Assuming that no apps, music or videos are being stored on the iPad and that the pictures are using JPEG compression then the iPad could hold over 100,000 pictures.
The iPad can hold about 5,500 songs, assuming you have no apps, pictures, or videos. There is no exact number, as there are multiple bit rates per song so it can change. I have 4500 on my 32gb touch with about 2gb of memory left.