First, since this is going to turn into a jailbreaking tweak question, I've moved it over to the Hacking section - get you more eyes on your question...
Now, some ideas. First, I'm not sure what exactly Windows8 does with pictures, but here are some things with Cydia tweaks that might protect your pictures.
The first is PhotoAlbums+ ($6.99 USD). With it, you can create albums, on the iPad and within the Photo app. You can set a password on each album so that whatever pictures you want secured ... are.
Or, you could get a tweak called FolderLock ($1.59, USD) which will allow you to lock folders, spotlight, settings and multitasking.
Or, you can get yet another tweak called Locktopus ($2.00, USD) that will allow you to set a password on individual apps/icons.
Again, I don't know the specifics of the Windows8 process - might any of these be of interest? They are all in Cydia, and come in the standard Cydia repos.
Hope this helped. Let us know how you get on - or if you have a different idea in mind.
Marilyn