One: Do NOT use BMP files for sig pics.
Two: Do NOT use Geocities, Tripod, or Angelfire to host sig pics.
Two A: If you must use Geocities, learn the TXT trick.

TXT trick. Take your image, say, ninjaman.jpg. Rename its extension to TXT. ninjaman.txt. Now refer to it like you would an image, using the image tag of your choice. HTML, UBBcode, etcetera. It will show up as an image. Geocities will think you're just calling a text file, and people's browsers will interpret the data as an image (because it is one), and you're in business.

At least, until Geo corrects this oversight.

- Where it's always 1995 (or so).