Only 'new' photos show up. 'Old' ones, such as ones taken before hte restore, don't show up.
If you load your last backup after restoring then everything comes back (as long as the photos are still part of your Photo Stream). I happened to restore my iPhone 5 last night to clear up Other and everything in Photo Stream and all my streamed albums came back just as they were before restoring.
Now, if you're referring to not loading a backup after restoring, then you will lose Camera Roll and possibly streamed albums, but I'm pretty sure that your main Photo Stream will always come back if you sign back into your iCloud account (perhaps not though ... and maybe this is what you're referring to?)