At boot time, your Hackintosh's bootloader can only display the basic resolutions programmed into your graphics card; these are known as VESA modes. VESA resolutions usually aren't widescreen, so if your Hackintosh uses a widescreen monitor, all of the images on your bootscreen may be stretched and distorted. This can be fixed by changing the VESA modes in your graphics card, but it isn't easy.
OS X Mountain Lion will be released to the public this July. Though the front-end of OS X will remain mostly unchanged by this impending update, it does include a few Hackintosh-friendly updates under the hood.