PhotoAffix (BETA)
To be clear, redistributing this app as your own without any sort of credit is NOT permitted.
This app is still in beta! You can download the APK to try it out.
You can opt-in to beta testing on Google Play too.
I commonly use Screener to make device frame art, and I put the results side by side to make one showcase image for apps. PhotoAffix will help you with that. Plus it's open source.