Is it okay to have a whole website featuring Flickr pictures with due credits to their owners? Should one contact each photograph's owner in order to use their picture even with the intent of linking to the owner's page? I've seen many blogs occasionally using Flickr pictures of others, but what if I make a website just about them? Thank you!
Most pictures on flickr are covered by a creative commons licence - which means you can use them - however, some flickr users will have opted for a different form of licence, so you need to check for the photos you intend to use. http://www.flickr.com/creativecommons/
Commercial I define as "Use for a business purpose", where by, if I was to do this, I would request permission from the owner of the piciture. However, if its for personal use, I'm sure it wouldn't be a problem. If I was you, message them and ask if you may use it, you do run the risk of Copyright.
You should always contact the creator or else you might get sued with CCommons since Flickr is protected by cc (i.e. creative commons) so be careful ok