Tumblr has a selection of free and premium themes, but you can only apply them to your blog and not the dashboard. To fill this void, there are browser extensions such as Stylish and Nice Tumblr that use scripts to alter the Tumblr dashboard. Themes installed via these scripts are only visible in the browser with the extension installed. To revert back to the default Tumblr dashboard, you have to disable or remove the custom theme using the browser extension from which it is activated.

Stylish on Firefox or Chrome

Step 1

Click the "Stylish" button on your browser, and then select "Manage Styles" from the drop-down list if you are using Firefox or "Manage Installed Styles" if you are using Google Chrome.

Step 2

Scroll through the list of styles and locate the customized theme that is applied to your Tumblr dashboard.

Step 3

Click the "Disable" button to stop using the customized Tumblr dashboard theme, or click "Remove" to remove the theme completely.

Nice Tumblr on Chrome

Step 1

Sign in to your Tumblr account and access the dashboard.

Step 2

Click the "Nice Tumblr" link displayed on the dashboard next to the Search Tumblr box.

Step 3

Click the first thumbnail to remove any themes and revert to the default Tumblr background.

Step 4

Click "Dashboard" to return to your Tumblr dashboard.