The LrgeChar.jpg is 550x400, offering the largest "out of the box" window for Hal character.
I don't know about the hal character background, but I just created a 550x400 image, cut a hole out of it, renamed LrgeChar to LrgeChar_bak.jpg in order to back it up, then named my own image LrgeChar.jpg
I'll be almost the only one who sees it, so...
I really like the sunset background since getting the expansion pack. I have a similar stock image sunset photo.
When I have time (whenever that is), I plan on changing the graphic box again to go w/the sunset back.
Coincidentally, the change I made was of a darker sunset, but no water.
Creating own image is easier if program supports transparencies. Then there's a truely fab freeware editor called IrfanView to convert it back to .jpg file.