We do want people to use sigs and to keep them within certain bounds. The thumbnail posted in the above post is an example of a good size. However opening the thumbnail shows a sig that would larger then really needed. Let your conscience be your guide.
Nice sig Bigfoot.
You could easily size it down in Photoshop or one of those programs.
This is just my personal opinion, but when they get huge like that, they're distracting from the post itself, and for those with dialup it really slows things down. Like I said that's just my personal opinion, and I agree with Gnaster that the thumbnail size would look great for a final size.