I use poser in much the same way, as a reference or sketch artist to begin an image.   It would depend on the type of clothing you are looking for for reference.  Some sources I use:

For medieval renaissance clothing, look up renaissance faires, and check their vendors, they usually have tons of pictures of their apparel, usually modeled.   Outlet and costume stores are also great references for these as well as looking up on the web sites for renaissance films such as "elizabeth" "shakespear in love" and so on so fourth.

For modern apparel, you can check out fashion sites for runway, or, online catalogs like J.C. Penny, Macy's, Lord & Taylor, and the like.