Gallery of Images to Overlay pictures example needed - Android

I'm a newbie on Android.

And I'm programming an application which should overlay a bitmap image over the picture on preview, then save it with the overlay on it.

However, right now it's working with just one image declared via ImageView on default activity layout xml file.

I'll need to load the bitmaps to be overlayed from a gallery of them, similar to the filter view into Instagram app:

Instead of filters, I'll put there the bitmaps I need to overlay on the picture preview, with the possibility to choose one of them and then take the picture obviously.

My question is, is there any example around that implements this kind of behavior?

I've looked for instagram-alike apps, but no success, only found some open source versions for other platforms other than android.

Any suggestions?

Thanks in advance!