Under Options | Uploads, there is a field to limit the number of simultaneous uploads per person, and another to limit the overall number of simultaneous uploads. You can also reduce or increase the amount of bandwidth allocated to uploads. I believe it takes effect the next time you start up Limewire, so after changing the settings, you'll have to stop and restart.

There's also an option (somewhere, can't remember where) where you define your type of connection to the Internet. I believe -- although I'm not totally sure -- that Limewire deduces the optimum number of Limewire connections to create based on your type of Internet connection. It used to be that you could specify on the Connections pane how many Limewire connections you wanted, but that was removed, because too many people were abusing it and setting up 12 Limewire connections with a modem connection to the Internet.