Ah, I see. This does get me closer to how I would like the images to spaced, thank you! However, it also greatly limits the number of images per row, which ultimately reduces the number of images that are visible at the time.
If possible, I'd like to get around, say, 50 decently-sized images visible at once on my monitor. Ultimately, I don't think that'd be possible without being able to directly reduce the vertical spacing between each image. I figure that Launchbox spaces things this way just in case you happen to have some games that use DVD boxart images, or something similarly-sized. (Though, every image that I'm using is the same resolution, so I wouldn't ever need spacing for a portrait image.)
I did manage to get a lot more to display at once by increasing the aspect ratio (to 1.04) and then using Ctrl - to zoom as far out as possible. That might be helpful to anyone else that's trying to do the same sort of thing.
I haven't had any luck fiddling around with settings to reduce the vertical spacing any further, so I guess this is probably as good as it'll get for now. Some new setting to reduce the spacing would be really nice, but this is a pretty decent quick-fix.
(Oddly enough, there's still some free space to the right, but increasing the aspect ratio any further causes the image to go to the next line. I'm guessing this is for people that have the scroll bar on, or something like that.)