What do your houses look like currently? It's helpful to have a starting point so we know where to go from there.
p.s. The design of that "M" in my signature was my doing (under a different username that I lost the login to), so there's at least somewhat of an example. I generally try to go with colors that are somewhat similar to each other, but with a reasonable amount of contrast so they still stand out, but some people are more adventurous and manage to find really contrasted blocks that somehow work together.