Well, Tumblr is not quite a blog in the traditional sense; I think of mine as a snagfile to post quotes and great photography and miscellaneous quips from everyday life, since the way Tumblr is set up it’s inclined towards fleeting thoughts as opposed to longer, content-heavy articles. This is great for me when I don’t have the patience for a full-length blog post.
This can be a good or bad thing.
@rskaletz It should be relatively easy to customize nearly anything; if I remember correctly they let you delve into the HTML code, so if you’re comfortable with that you could easily add pictures and change around your header image, like you said, and also change layout, fonts, color, et cetera…add things like a ‘Read More’ link or a ‘Related Posts’ type of thing…I’m assuming you have a basic knowledge of HTML/CSS for this?
You might like to check out an ebook on customizing Blogger templates if you want some in-depth information on what can be done. The site has some other helpful information about what you can do.