I have 3 apps that I love to use and have used them for years with no problems.
Go to Google Playstore and do a search for "HD Wallpapers" Be careful because lots of these apps have spam and ads
Here are the ones I like.
1. Backgrounds HD Wallpapers by OGQ
2. Backgrounds HD Wallpapers by Stylem Media
3. HD Wallpapers for Android by PowerApp