Move the image a bit up so that it aligns with the first text box.
I've been thinking about this and its a bit tricky. A solid gray border looks odd on images that already have a border (it would also merge with any image with a gray background but that is less of an issue since the area around that is white). A shadow might work but we don't use that anywhere else and it looks out of place.
Since the image is sandwiched between the translation interface on the left and the edge of the screen on the right people should have some idea of how much they can write. But, you're right, for finer judgements this might not be enough.
Would this mean that we'll have the image inside a larger box, or will the image fit to the box and we'll only get a small border?