I just had a thought about large picture sizes. Cameras now have huge resolution and it is predictable that your end user of this application is going to try and start with a picture that has a equally huge file size. While a very wide range of file sizes are accepted by bootsplash, I have made several pictures fail in my testing by using pictures >750kb. I don't know the exact threshold.
While you could use Imagemagick's -quality option to reduce the filesize, you would also have to come up with a test to make
sure you are only reducing those that need it and determining what maybe too much of a reduction.
I think the simple solution would be at the front end to post some instruction that the user should make sure they are starting with a picture that is <500kb say.
You could also use a bit of script like this to show the user the size of the picture they have choosen. Even warn them that a large size will slow boot time or may not work at all.
identify -verbose imagename.jpeg | grep Filesize
Anyway, Great little application.
Here's an example of a picture that did not work for me until I reduced it's file size with the -quality option.http://spiritual-art.info/wallpapers/animals/1280/1280x1024_kittens4.jpg