Image variable BBCode

[Bellardia]

You could detect each character as an image like you said.
Such as letter
a = 'firstimg.png'
b = 'secondimg.png'

so [ul]aba[/ul] would return the 3 images in a row.

I was hinting more towards how to format the images? Are they all the same/size dimension, and will they all fit on a single display line or will some have to appear ontop of eachother when formatted because they're too large.

Such as
one line would have images ababaaab and they would flow over to the next line with images bbaba etc.

Hope that makes sense?

Either way it's still possible, you'll just have to include some math as well to calculate line widths and when to skip to the next if its too large.