Well an app isn't really needed, plus you can run into mac/windows issues. The idea I've got is you can set a DVD to autorun the html file which is on the disk and they can just view the images there and have a link to the 'file explorer' if they wanted more info.... like I say it's one of those ideas that pops into my head and it's not really important.
This isn't for concepts this is for supplying final artwork to clients, think renderings etc, so they can use it as they wish.... and would be completely internet free. I supply video/images to clients but I never give my cad files unless it's in the contract so this approach to 'presenting' the final work on a dvd just seems like a good idea

It would basically go something like this
- I copy all the files to folder on disk + a html file that has all the code sorted to 'make a gallery'
- the client gets the dvd and sticks it in their drive, it autoruns the html file which then allows the client to see the 'jpeg' files so they know what to pick... yes I know most file explorers have thumbnails, this just seems more professional

- the client clicks a link at the bottom to be taken to the 'high res' folder and selects the required file or each 'jpeg' has a link underneath to download the high res one...
I know the idea is possible, because I can do it all manually in html, it's just is it possible to do it without having to hand code in each of the files, that can get tiresome after a LOT of files, like that php idea up top.... I suspect it is but I haven't seen the idea anywhere...