What info in your database determines which option is needed?
Insert From device can specify a number of different input options--all documented in FileMaker help. They include inserting a photo from the front or back camera or from the camera roll. They include inserting a signature.
so you can use one Insert From Device script for inserting a photo and a different insert from device step for inserting the signature. But how you determine which to perform in a given instance will depend on the design and intended function of your database. You might, for example, have one button to tap for inserting a picture and a different one for inserting a signature. But you also might be using completely different layouts for each insert and then you only need to detect what layout is current in order for the script to determine which Insert From Device step to execute.
I didn't suggest that you use two different fields but that you could use two different buttons. A popover can be set to open that displays the two buttons and the result will look very similar to what you show in your screen shot.
But you may be remembering just having the user tap the container field--which then opens an insert dialog where the user selects the insertion method.
Ah yes.. popover button with options is not a bad way to go... My apologies for mis-reading you... Seems like a couple of extra steps for each one of my fields, but it works.