Hmmm... I'm fairly new to this photography lark, but I live in the peak district, so can possibly help! For rivers/lakes it's got to be Millers Dale and the Goyt Valley. Goyt will also provide old growth forest and and Erwood Hall (some interesting ruins), small waterfalls and good views. Take some bread to the Anglers Rest pub at Millers Dale and the trout will jump out of the river for it right by the pub carpark.
Tideswell is right next to Millers Dale, with some interesting old buildings and architecture.
If you fancy a real lighting challenge, there's the Blue John caverns everywhere you bleedin' look, and the old collapsed road at the bottom of Mam Tor.
For small "quaint" towns/vallages (aka inbred... dammit... think, don't type) Flash is the winner for webbed fingers and 100 people with 3 surnames between them... I would stick to Castleton, Eyam (former plague village with a facinating graveyard... there's an advert) and Bakewell.
For Stately Homes, there's Chatsworth, complete with it's gardens, river and extensive grounds and forest.
Hope that helps (and doesn't offend too many...)