I received a request recently from someone asking for help on how to change his Google Blogger template without losing his old template. The 2nd part is really easy, you just download a full back up of your blog to your hard drive, this feature is built into Blogger.
Once that is done finding and configuring a new template may not be quite as easy, there are lots of free templates available but you are at the mercy and skill of the person who put the code together and some are better than others, so you could be in for an easy ride or it could turn into a nightmare. The physical process of changing a template is very straight forward and is described on my blog Moulin Website Design for anyone who wants to know. But take care and check you are really getting what you want.
On the other hand changing from one of Google’s own templates to another, really couldn’t be simpler and again this is explained in the same post.
So have fun, a unique looking blog is always nice, but don’t forget about the functionality and if you want my advice go for a self hosted WordPress Blog.