If you know CSS, you can make your own themes to customize the way Itsy looks.
A theme is a folder named with the extension ".itsy". You can name the folder whatever you want as long as it ends with the extension ".itsy". We'll call this folder the theme package.
A theme package contains the following:
The Info.plist property list is an XML file which contains the following fields:
The CSS file that defines your theme must be named "styles.css". It is just a regular CSS file. One important point is that you must provide a scrollbar style. If you don't, Itsy will get confused when a user switches between your theme and others. To style the scrollbar, use the Webkit scrollbar CSS pseudo-elements.
You can use a tool called WebKitInspector to see Itsy's HTML. Here's how:
defaults write com.mowglii.itsy WebKitDeveloperExtras -bool true
Installing a theme is very easy. Once you have created your theme package simply double-click it. This will copy the theme package to Itsy's Application Support folder. Itsy will launch with your new theme activated. That's it.
To get you started, here is a sample theme: Itsy Light. If you use this theme as a starting point, remember to edit the Info.plist file and change all the fields.