I set the ToolTipImageSource and ToolTipFooterImagesource properties of a Ribbon Command to a PNG 16x16 image.
However the image gets streched and apears about 5 times larger, even tough i don't have a lots of text in that tooltip, just one line.
Same with the ImageSource property for a command used to display an application button - the round one in the left top corner of a window. Image is PNG 32x32 but appears very small.
Ale done using Office2007Blue theme.