I'm from Cleveland, but don't get back much. If I did, I would be photographing the industrial sites and former industrial sites around The Flats, though many of the warehouses in The Flats are now restaurants and such, so I'm not sure what it looks like these days. I've always liked the area around the Cleveland Museum of Art and Severance Hall--many interesting 19th-century houses around there, and do visit the museum and listen to the Cleveland Orchestra, which are two of the city's main attractions. I've never been to the Rock-and-Roll Hall of Fame, but you should definitely stand on a public sidewalk with the biggest camera you have and photograph it as a matter of principle (there was an important lawsuit about the right to photograph buildings from public vantage points in which the Hall of Fame was the losing plaintiff).
I never spent much time on the Lakefront. If you're interested in natural sites, get a map of the Metroparks, which circle the city. When I have gotten back in recent years, I've tended to gravitate toward Chagrin Falls, which is a nice little town East of the city with a town square and a falls that used to run an old mill. It's also fairly close to some Metropark access points.