Visualization is a skill--and like any other skill, it must be practiced if you want to get good at it.

When you're falling asleep, or bored, or whenever, try to hold an image in your head and see how long you can do it. Something simple (like an apple) works best at first. Try to make it as real-looking as possible. Another good one is a burning candle.

As you get better, work your way up to more complex objects. Then it really will seem like it is painted on your eyelids.