Quite interesting question. Yes, you are allowed to buy clothes with Bitcoins. Not only the clothes, you can buy anyone. Some of the people already using Bitcoins for online shopping as most of the shopping sites in all countries accepting the digital money to avoid extra charges.
A lot of sellers who currently use bitcoin as one way of payment. Although only a small merchant but this is very meaningful because this is a good start to introduce bitcoin. We can buy anything with bitcoin, just as we use a conventional money as a means of payment. Clothing is a primary need, it is great for bitcoin development to be used by many people.