Its very annoying when people aren't original. To me, part of games like Blockland is to be creative. People should take ideas and craft them into their own, but they don't. It can be disappointing if nothing else. Although having said that, part of the design process IRL in professional situations like web design, etc, is to look at what people have designed before. So maybe your friend is just trying to find his own style of building.
Though you can complain, you don't really own the style. Unless he is trying to make commercial use of a unique design you had protected under a design patent, he isn't exactly in the wrong.
It is just a virtual lego build that few will probably see, after all. Even you sound done with it.
Yeah, its a bit douchey. I hate to be corny, but maybe in this case, you really should be complimented that your friend looks to you for build styles. Don't let it ruin a friendship, he'll find his own style eventually.
