Version 1.04 posted.
Video demo is
here. (as usual, switch to HD and enlarge for best results)
This update is a bit of an odd one. I've added a major new feature, but I'm not entirely happy with the algorithms, so it looks like there will be a v1.05 one of these days. But still, it's an improvement over 1.03.
What's New?This update adds a plugin for Fiji (a free photo program).

The plugin will take this...

and with the click of a button and a short wait, produce this...

In addition, it will measure the dimensions of the
stamp. Again with the click of a button, these dimensions can be imported into the
Stamp Album Page Generator Spreadsheet.

And when you insert the photo into the spreadsheet, the dimensions auto-populate.

So overall, it's now easier to process the scans (no more manual realigning in Photoshop) and get their dimensions (no more trying to find where I laid my ruler).
There are a few limitations for which I haven't yet found a workaround (hard-coded scan resolution being the big one), but overall, a neat little addition to the package. I also need to work on the processing algorithms to make them faster and more accurate, but that's a longer-term goal.
Software RequirementsScribus (free)
OpenOffice (free)
Fiji (free)
Java SE (free)