It occoured to me to see if the signature graphics were available in PNG format (rather than GIF) for PNG's smaller data-size properties.

From the suggested signature graphic URL I altered the filename extension to be .png instead.
The altered URL did not return an HTTP 404. I was pleased.
After checking the actual data sent to confirm it was really a PNG image (not just GIF sent as PNG), I found that PNG formats were indeed available. I was more pleased.

However, I then noticed that the data-size of the PNG versions was actually larger than that of the GIFs.
After some checking in an image editor, it seems the PNGs are in RGB mode, resulting in the larger data-size. I was less pleased.

After some quick experimentation with indexed colour mode, I found that indexed PNGs (the most comparable to GIF) are indeed of smaller data-size than GIFs (based on the signature graphic content). Indexed PNGs are about half the size of equivelent GIFs.

First request: when signature graphics are requested in PNG format, send PNGs using indexed colour, which results in less data to send as PNGs achieve higher compression ratios compared to GIFs.

Based on the first request, would it not be sensible to advertise that people use the PNG versions by default, instead of the GIF format?
Support for PNG is wide-spread, and implementation of PNG is less problematic than GIF anyway.

If for no other reason, to reduce the amount of data being shunted around while providing exactly the same image content.

Thoughts and input would be appreciated.

Any comments from a Dev/Admin on this issue?