Blog Personalization Customization?

I've seen a few homeschool blogs (as well as others) that have their blogs personalized. I don't mean some really cool background they got from some other website. I mean their very own personalized background and graphics.

Like....ok, I'll use this blog as an example.

We now have our school crest completed. I'd like to have that either on the top left corner, top right corner, or one on each corner with a banner in between with the name of our homeschool. With the background and other customization being the colors in the crest.

But I don't know how to do that.I know how to MAKE the graphics, I just don't know how to code it so they go where I want them to go.

Any suggestions?