Insert a picture or symbol over container field: is it possible?

Hi all

My problem is in Filemaker Go

I take a photo with iPad or iPhone in a container field. Now I want to insert a symbol in a point over the photo (over the container field). The symbol maybe a character or png transparent picture. This symbol have to a ID field inside database linked to data. I can have many symbols over container field. It's like a geographic map with symbols over the map at specific coordinates. I want to substitute the map with normal photo.

I tested many solutions but nothing is good: the most near is to create a trasparent grid over the container field and any cell of grid is a clickable boolean field : 0 is transparent, 1 is red transparent and this field is linked to data. This solution is partial.

Now Filemaker Go 13 has base64 encode/decode data and it is possible to insert a photo in container field and view it in a webviewer field. There is show/hidden object function. Is there a solution with interactive javascript in a webviewer to insert a base64 symbol and linked the object to data?

Other methods??

Thanks in advance