Like any regular blog, you’ll want to personalize the feel of your page. At Tumblr.com/themes, you can search through nearly 1,300 options for premade looks. Many of the choices are available for free, but there are premium options that range in price from $9 to $49. When you purchase a theme, you can also donate to a good cause. After you’ve entered your credit card information, an optional pop-up window will ask you to donate $1 to the Red Cross, Doctors Without Borders or the Electronic Frontier Foundation for the use of that theme.