Where and how can I ask for permission of product images?

For the large media companies, there's usually a formal process - a) identify the copyright "owner" ... this may not be straightforward as the site/location where you sourced the image from may only be a redistributor

• b) some basic steps are look at the metadata for the (C) sign, trademarks pasted over the image are another strong signal.

• c) work out what "rights" you are seeking. Some may be covered by fair usage (eg criticism) or their copyright can be extinguished/exhausted through derivative works (caution ... some recent caselaw looks like limiting the deriviative works justification)

• d) find out the office or person responsible for licensing rights ... whilst I am an IT/IP specialist, media law is not my forte but I suspect there must be some sort of industry directory or yellow pages listing the contacts

• e) negotiate ....

Some alternatives ... depending on the industry you are in, there may be blanket copyright clearance industry bodies where you pay a fixed fix ... however as you specifically mention cover art I suspect not. The other route is to find a clear exemption (eg criticism) and get your lawyer to write an opinion that you are covered ... this becomes part of response form letter if you get a DCMA takedown notice. Thirdly, since some sites encourage social networking activities, try to figure out their link policy and document how you notified them, and that you are following the policy. This can get painful as the legalese and copyright maximalist positions some media companies follow make it (perhaps deliberately so) onerous to value-add around their franchise.