It dates from the Wireplay incarnation of MUD2, and is a screenshot of the game as it looked in the Wireplay-specific client back then. Sadly, the people who wrote it only provided an executable and they closed the company afterwards, so no-one uses this client today. They don't use Wireplay, either, come to that.
The mouse mat was one of two batches we had made (the first one sold out). I kept this one because it wasn't printed properly — there's a white line down the left edge where it doesn't align — so I couldn't really sell it.
I'd eBay it as important MMO historical ephemera, except that it would raise less than the postage cost to send it to the winner.