I will answer you with an exceprt of Grand Master Chen Zhenglei's book : Tai Chi for health:
" After a period of practicing meditation the inside and the surface of your body may experience various sensations such as cold, hot, light, heavy, solid, tingling, bulging or tickling. Initially, the tip of your fingers and your feet will be the likeliest place to get these kinds of feeling. Then the stomach and the intestines may possibly experience some sensations, with your body or part of your body feeling cool on the surface and warmer inside. Some muscles may begin to shake and feel tingly. All these feelings depend on the individual with some people experiencing strong sensations and others simply feeling relaxed and calm. Sometimes images may appear in a similar way to when your mind is thinking toc much. These can range from a mountain or a lake to even a person. In this case you should not be concerned. Also you should not be very anxious to see these kinds of images, because they are not real, they are a creation of your mind.
As those kind of images occur, you should keep your mind still not paying attention to them. Focus on your dantian. Let the image disappear itself. In Chinese we say " Treat strange things as not strange. Then the strange things will become normal". All these kind of images will disappear and your mind will become cleared as your level of meditation improves. The perfect stage of meditation is when no thoughts remain in your mindand it is as still as water with long, deep, smooth and conscious breaths, naturally coming only from the lower abdomen. Your mind will drift between completely absorbed in the moment or absolute concentration"
Tai Chi For Health , Grand Master Chen Zhenglei and Master Liming Yue : you can find this book here
http://shop.wbpay.com/epages/es109490.s ... 09490_shop It is Master Liming Yue website in UK