What would be the challenge of using non-traditional channels to promote traditional products?

You are talking for the most part about guerrilla marketing, which is the promotion of products or services in non-traditional ways.

There is much to be said for guerrilla marketing, especially for a small business operating in a crowded marketplace. Simply, the main challenge is to stand out from the crowd, and any non-traditional channel you can use is fair game because it will differentiate you from competitors.

As to what those channels might be, and the challenges involved in accessing them, there are no limits except those of your imagination. However, keep in mind the purpose of the exercise, which is to get your unique product line seen by potential customers.

Therefore, you may want to think about who your target customers are, and where they gather. If your clothing is sportswear, for example, have athletes at relevant sporting events wear your products so customers can see how they look; this is a common technique used by bicycle clothing makers. If your target market is young people who go to nightclubs, outfit some club goers with your clothing and have them circulate at various clubs and hand out cards so those interested will know where to find them.

This is generally called "buzz" building, and most recently has been raised to the status of a fine art by some marketing service companies that arrange these kinds of situations.