Take a look through the 20 we've gathered below for you, and you are guaranteed to find one that will inspire you to change the look of your Tumblr account.
Have a favorite Tumblr theme? Tell us about it in the comments.
1-Column Tumblr Themes
ColorBars - A dark, but very legible, theme with colorful date markers out to the right side producing a color bar effect.
Dead Simple - The name really says it all with this 1-column theme. White, open, left aligned leaving you lots of open white space on the right. It makes for quite a striking theme in its simplicity.
Terminal Flashback - A fun retro theme that harkens back to the 1980s/early 1990s of the Internet by recreating the look and feel of a terminal interface.
2-Column Tumblr Themes
Blange - A black 2-column theme with nice shading that progresses out to the sides. Uses a mixture of orange and white text to make a very readable dark theme.
Chrome - A theme that pays homage to the Google Chrome browser while keeping all of your information front-and-center with your info, who you are following and more.
Cliché Theme - While it doesn't make any groundbreaking strides in design, that's kind of the point. Cliché Theme is all about feeling uninspired, but does a great job of creating an "I didn't really work at this" feeling.
Content is King - A simple, clean, theme that puts the focus on the content of your Tumblr account and has a space in the header for your "About" information.
PressRow - A very nice WordPress-to-Tumblr theme conversion that allows for the addition of Twitter and Flickr streams in the right column.
RedSky - More of a traditional looking blog theme, RedSky includes Google AdSense placements at the top of the content column, and a larger one in the sidebar.
Roboturner - A nice 2-column theme that marks the different types of posts you can do on Tumblr with icons, and a customizable right sidebar. To see how much you can change it up, check out the official Mashable Tumblr.
This Is Not A Template - A clean and very open 2-column theme that puts your info on the left and gives you a nice footer with links to your social profiles and other info.
3-Column Tumblr Themes
Box Factory - Box Factory puts your posts into, well, little boxes. If the post is too large to be displayed in its entirety, a scroll bar will appear. The top row is reserved for information.
Classy Bigfoot - A 3-column theme that social media junkies are bound to enjoy because there's plenty of space to add links to your favorite profiles.
Graph Paper Theme (Remixed) - This 3-column theme is fluid width and gives you plenty of room to add various widgets and put your information such as RSS upfront so that it's more accessible to your readers.
Griddle - Griddle is a compacted 3-column that gives you things like your latest Twitter activity and Flickr images in the left hand column, Tumblr info in the middle and your actual posts on the right.
ScreenShot - A great theme for anyone wanting to show off a sampling of their work, but directed specifically at web designers to be able to show off examples of the sites they have designed. You can click on any of the images for a larger view.
Twittr Inspird - Just as the name says, this theme is inspired by Twitter and gives you a similar "Following" area in the right column as well as a space for your "About" info. In the left column you have the ability to include your latest tweet.
Miscellaneous Tumblr Theme Layouts
Museum - All of your posts get put into little boxes, and if there is more to see than what can fit, a red plus sign shows up on rollover which will take you to the full post.
Photo Board - A really intriguing theme that sets up your Tumblr to look like a photo board made out of cork. Each entry gets posted on the board like a photo someone hung up with tags and information visible only on roll over. Can be set for 2 or 4 pictures per row.