With the small tool, the display format of the thumbnails in the taskbar can be changed very quickly.

Windows 7 Taskbar Thumbnail Customizer
Superbar tool

Windows 7 Taskbar Thumbnail Customizer allows you to customize the thumbnails of the Windows 7 taskbar in detail. The size of the thumbnail, its spacing, top, bottom, left, right spacing and mouse delay time can be changed.

The text height can also be easily adjusted.

After the settings have been made, simply click on Apply changes. The Explorer.exe restarts to apply the changes.

More information about the Windows 7 Taskbar Thumbnail Customizer in the article
 Windows 7 superbar tool