"Swag" also means "accessories," "valuables," and "loot." These are old definitions, however. The US has stopped using "swag" in this sense about 15 years ago. "Swag" is also short for "swagger" which azzipog defined nicely. In the case of loot: "That thief absconded the house with swag." meaning the thief took the valuables from the home he robbed.

swag in chinese is like 风度，气质, 酷. Mikey gains swag by swagging up, :D. 中文流行的说法应该是好有型哦。

Swag on the t-shirt is a short for swaggering. This word does not mean anything nice. It is 大搖大擺的架子. So they think it is cool. Also swag means a piece of cloth draping over something. For all other meanings, see http://www.thefreedictionary.com/swag

Sorry I am not the best at Chinese, but I will attempt to explain in English. Swag describes a level of "coolness". It can be seen in one's walk, in their talk, and their poise. Used mostly by thug wannabe's or sarcastically by others, it acts primarily as a noun. "He has got swag".