Normally ovos creates expressive screenshots for the release in the different necessary sizes for the store entries. However, it is also possible to make the screenshots even more beautiful, as ovos has done with its own "ovos play Teams" app, for example.
However, there are some things that need to be taken into account for this - we need these graphical elements in numerous different sizes and additionally, there are quite strict rules, at least at Apple.
The Rules
The smartphones shown must not be Android smartphones, but must have either iPhone or iPad frames (otherwise Apple will reject these screenshots when checking the apps).
But the iOS screenshots can be used 1:1 for the Google PlayStore as well
The screenshots must show content of the app - Apple recognizes when things are shown on the screenshots that do not exist in the app at all.
The Sizes
For iOS AppStore
6.5 inch: 1284 x 2778 pixels (normally in portrait format)
5.5 inch: 1242 x 2208 pixels (normally in portrait format)
12.9 inch: 2048 x 2732 pixels (both portrait and landscape mode are possible, but don't mix it)
For Google PlayStore
Basically, no new screenshots are necessary here. For the Google PlayStore, the 6.5-inch screenshots are used for the phone screenshots, and the 12.9-inch screenshots are used for the 10-inch tablet screenshots.