Our division wanted to standardize the email signatures. We created this jQuery Email Signature Generator, which was used by our staff. Everybody was able to implement email signatures by themselves within three days.
The instructions to implement the signatures are there, the users seem to understand them easily.
The layout is very simple, we avoided multiple columns to make it more compatible with most email clients and small width screens.
We tested the signature and the implementation process. Everything has been working fine for the last year.
We found helpful to define the images width and height, and to use inline styles to avoid compatibility issues.
This tool only work in Chrome, since we experienced issues when copying/pasting from other browsers.