Oh man those are awesome. I suddenly have the urge to use LEGOs as stand-in minis! Do they sell just LEGO minifigs without the bricks?
3 of the 4 players in my game use a fancy metal figure painted by my buddy Mike and the other is using a D&D plastic figure which is a pretty good representation of his character. When I play LFR games I use a plastic halfling rogue figure that came out of an old D&D box Mike had and in the current Encounters season I'm using a plastic bug mini that the DM had to stand in for my Thri-Kreen battlemind.
Mike actually had two old D&D boxes that happened to have about 8 Kobolds between them, so I've been making use of those in addition to these awesome little tokens that were included in the D&D 4e Starter Kit (we bought this just for the tokens, actually). The tokens include orcs, kobolds, beetles, skeletons, stirges and a few others, but most of the time I'm just using them as a placeholder and telling the players what they should really look like. As an example, the party currently has a horse-drawn cart to bring them around long distances and the horses are represented by a dragon, a gelatinous cube, a dire wolf and a large drake (we sometimes shorthand this to just one token per pair of horses).
http://web15.twitpic.com/img/1218128...7a6b8-full.jpg
Here you can see the cart with one pair of horses leading it, the other pair were incapacitated. The paladin, Cyrus, decided to head out to investigate and found himself a few kobolds waiting in ambush. At the point this picture was taken, it was time for initiative to be rolled.