One of the largest resources of photos of orchids is Flickr... there are several groups solely of photos of particular types of orchids. If you haven't already seen them, check them out:
Flickr: MASDEVALLIA & related orchids - over 1,000 photos
Flickr: Phalaenopsis Orchids - over 1,000 photos, though it seems some people have posted other types of orchids as well.
The companion group for Eric Hunt's Orchid Species Site.
Flickr: Orchid Species Photographs
And just 'orchids'
Flickr: The Orchids Pool - over 23,000 photos for your browsing pleasure! Though again, the photo pool needs to have some non-orchid photos cleaned out.