Images are loaded by gdk_imlib.
The checkmark brushes were done by Martin 'XEN' Huttenloher, and their original IFF versions are distributed in the MUI-user archive.
The pink background is a modified Gimp pattern.
The button gradient background comes from the GTK 'Gradient' theme.
If it looks like bad taste for you, don't panic : you can configure everything :)
Some pre-0.1.15 screenshots, but fun enough ...
Real 0.1.15 screenshots, at last :)