By text framing, I mean the text frame within the AutoShape. Let's say
you're using a Flowchart Decision AutoShape (i.e. a diamond). The
textframe is the largest rectangle that will fit inside the shape, so
for the diamond, the text frame is much smaller than the shape itself.

Since picture are rectangles, I would need to to use a rectangle (or
Flowchart Process) AutoShape to contain the picture. Since the default
textframe for the rectangle AutoShape probably won't match the area
that I want to add text to, I would need to play with the internal
margins.

It's not perfect, but it may work. I'll need to play around with it
some more.