You can download the officially supported themes from the WinRAR web site at.
If you want to install themes in WinRAR, then you can use these steps: What many people perhaps do not know that WinRAR also supports themes – a set of icons that can replace the default icons in the WinRAR toolbar. There are many reasons for this change – better and faster compression algorithms, support for more archive formats, very strong encryption and many more. But WinRAR has now become the most installed archiving tool for Windows computers and is enjoying the same popularity as once WinZip did. Back in the 90’s, WinZIP used to be the most popular file archiving utility for Windows users.