If you already have your character's big dialog image, you can resize it to 32 x 32 pixels and edit it with GIMP or other editor to make the sprite look nude. Doesn't have to be perfect, because it's pixels.
For example:
Oriana doesn't have a nude sprite, but I made one by resizing her full image to a 22x32 image and editing the pixels.
Original resized: 
Edited nude: 
It's not perfect, but I only spent an hour or two on it. You can try to do similar with your character to make the nude sprite.

