Also, you can upload images to use in your CSS.
Starting from v.5.2.x the add-on supports "Webmaster mode".
Starting from v.5.3.3.x the updated Webmaster mode allows editing text labels, adding custom CSS, moving layout blocks, easy picking the correct template files and editing them right on the storefront, i.e. all tools for making basic design changes are in one place.
When logged in as administrator, go to the storefront and make the changes using the design tools panel.
The "Theme Tweaker" will create a new add-on and copy a custom template - i.e. everything you had to do manually with the "Custom Skin" extension in the earlier versions.
In addition to the unbeatable convenience of making changes on the fly, you may rest assured that every tweak you implemented with this tool will be saved correctly in accordance with the OOP paradigm. In the other words, your changes will NOT break the upgradability of the store you modify!