I can copy one image to the pasteboard like so:
UIPasteboard *pasteboard;
pasteboard = [UIPasteboard generalPasteboard];
UIImage *image;
[pasteboard setImage:image];
How can I copy two or three images to the pasteboard?
[[UIPasteboard generalPasteboard] setImages:[NSArray arrayWithObjects:firstImage, secondImage, nil]];
I think this is all you're looking for. It is also possible to set a single image with multiple types (PNG, JPG, etc.) so that it is more likely that another application will find a usable image.
~ Good Luck