Apple - What's that site that frames screenshots in iPhone/iPad/Mac stock photos?
It sounds like you’re describing PlaceIt.
Here's what I found. Some are free, some aren't.
- placeit.net
- agicmockups.com
- psdcovers.com/category/action/mockups/apple
- appdemostore.com/frameapp
- graphicriver.net/category/graphics/product-mock-ups/displays
- picapp.net
- Scenery
PlaceIt is really powerful if you can afford it. But I like Frame App - it's free and fast and works well. No fancy backgrounds, just mockups.