By launching the Windows Sidebar Styler implementation, which will give this dialog box that gives you a list of all elements in the field. You can select the themes and preview on the right.
The big Play button will apply style, but you must load by clicking the button to the right of "Load a sidebar Windows Style," which opens a dialogue for selecting files so you can choose among different themes.
There are a lot of issues that come with the application, or you can find more items to WinCustomize Gallery.
If you click on the More button in the dialog, you can even select an option to make the sidebar size.
Once you select this option, you can resize the sidebar like any other window. You'll notice a new option of "blocking" Sidebar, which will prevent resizing, once you've chosen the size you want.
Another benefit is that this tool can load more powerful devices using WFP (Windows Presentation Framework).