Andee, if you're wanting hiking & picturesque-ness countryside (plus hills & trees etc) - you can't go wrong with most of the Yorkshire Dales or the Lake District, I'd say.
Some of our favourite places in the Dales (purely subjective!) and in no particular order: Burnsall, Reeth, Aysgarth Falls, Sedburgh (the Howgills - can be pretty remote!), Dent.
Some Lake District favourites (though we still have much to explore up there!): Dungeon Ghyll, Langdale area, Borrowdale, Keswick, Bassenthwaite, and you can't go wrong with the area around Ambleside of course (but it's a very busy, touristy spot!).
Also - you know the North Yorkshire Coast area isn't exactly flat - lol! What with all those cliffs!
You might not want to overlook the North York Moors area either - for this time of year, it's often even more spectacular than usual - with the heather in bloom.