Instead of refreshing the server list all the time, just click on "connect" and, when you get the "server full" message, click on "OK" / press "enter", then click on "connect" again.
This way you can keep the mouse over "connect", then click-enter-click-enter-click-enter...
But, yeah, a queue system would be great, like in Chivalry, but I guess it's not possible in Warband. Otherwise, we would have it already by now.