Have you thought about .cbr or .cbz? It's used for archiving comics. The file itself is just a load of JPEGs, either zipped (.cbz) or RARred (.cbr) together.
The JPEG files should be named in alphabetical order, ie the picture you want to appear first, should have a name that's first alphabetically.
CBR and CBZ readers are available all over the Internet. Might be suitable for your purposes. I've used it as a way of zipping up a load of JPEGs for viewing en-masse later.
To create, you just ZIP / RAR the JPEG files up together into one archive, then change the archive's extension to .cbz or .cbr . Pretty simple! I'm fairly sure it only supports JPEG images, unfortunately, though it wouldn't be a lot to ask for the reader software to support others.
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"hey let's educate the brutes, we know we are superior to them anyway, just through genetics, we are gentically superior to the working class. They are a shaved monkey. If we educate them, they will be able to read instructions, turn up on time and man the conveyor belts, sorted." #