mmm let me think... I lived in York years ago, and there are loads of great things to photograph round there - what sort of stuff you looking for?
York itself is ancient - dates back to viking times. The defensive walls are pretty impressive. There's also a ruined priory in the "museum gardens". If you want your "churchy bits" more intact then you can't really miss the Minster. Personally I lived in York long enough that the churchy bits, and other (actually pretty great looking) touristy bits kind of becaime invisible (and by July they'll likely be ruined by being full of pesky tourists). If you're into trains though - you've GOT to do the railway museum - its fantastic.
For more natural stuff - out in the country side, you can't really help falling over the stuff. I do remember going to "Brenham Rocks" - loads of rocks, cliffs and stuff you can clamber over - pretty fun, and I'm sure lots of good pics. It's a bit north of York (I think). Harrogate (also north of York) is a classic market town, but has a GREAT viaduct (again - handy if you're into that industrial revolution meets countryside think).
Leeds/Bradford are much more Urban if you're looking for grittier stuff.
Ian