Add Ping Localy(from Client Machine to the Servers) on the ServerBrowser and Server Description. Thats is a really missed function that could help

It seems like a good idea on the face of it but...

I don't speak for Gametracker, but that would be nearly impossible to achieve in my opinion.
You would have to somehow instruct the client side web browser to interact with the client operating system to issue a ICMP echo (ping) to the game server, and then send the answer back to Gametracker.

For security reasons, many game servers will block an ICMP echo request, as ours does. So there would be no reply from these servers at all.

As I have seen some players with pings from the same physical location, but on different ISPs vary widely (as much as, and even more than double), I am not sure an 'educated guess' would really be that useful either.

Another idea: let gametracker ping the servers.
I think gametracker has servers all over the planet. So it could be possible to use one (or more) server(s) on every continent to ping the gameservers and display pings from different locations for each server. This isn't like client-ping, but it gives some feeling for server's latency in relation to others.
Additionally these "ping-server's" IP adresses could be made public so gameserver admins could allow ICMP requests from these IP adresses if they want to. If a server isn't ping-able, there just no ping is displayed for these.