Tom knows better than I, so no, you won't find a beer glass variable to use in the brew sheet. Tom posted a file somewhere (I downloaded it last week) that lists all variables.
It took me a while, but I think I understand Tom's trick now, which should work for you as follows:
So you have many pictures to use for different brews, lets say they are named:
label1.jpg
label2.jpg etc.
If all your images are not the same aspect ratio I'm not sure if they will distort because of the img fixed Height and Width values (in pixels) in the brew sheet.
Go ahead and make the custom brew sheet as I described above.
You "take an unused field in the recipe" i.e. Assistant Brewer = $ASST_BREWER
Change:
<div class="glass"><img src='$GLASS' height='128' width='75' /></div>
To:
<div class="glass"><img src='
./$ASST_BREWER' height='128' width='75' /></div>
Note: ./ is a relative path to the current "Reports" directory, so if your pictures are somewhere else you need to modify the path.
Code:
Change:
<span class="item">Asst Brewer:</span> $ASST_BREWER
To:
<span class="item">Asst Brewer:</span>
Now in the Notes section of your recipe you can enter label1.jpg in the Asst Brewer box.
For your next recipe you can enter label2.jpg in the Asst Brewer box, etc.