Here a gallery of some sun tattoo designs.

It is common to stylize the corona of the sun in abstract designs.

Also many give the sun a personality. A happy moon paired with an angry sun, or a friendly sun paired with an aloof moon make nice tattoo combos; put one on your right hand and the other on your left hand so you can quickly express your mood of the day!

here's a photo of a sun tattoo with chinese characters

Here's an image of a black sun with orange and yellow corona. Use the top half for a rising or setting sun.

A classical contented happy sun is displayed in this flash. It would make a nice temporary or (converted to a monotone image) henna tattoo.

Here's a tribal design with a blue moon inside an orange sun in front of a blue/black star.

Or, add in some celtic knots and you've got a sun star design.

Or toss in the moon, some planets and other galactic stuff.

an angry sun with some bad ass flames, on an upper arm is shown in this pic.