That's a great shot. What you're asking is a like opening the proverbial can of worms, but here's some thoughts. First, if you're selling them all the rights, why do you think you need the copyright? Its a good idea to keep it if you can, but if you're sold them all the rights, what practical use can you make of the copyright? Read on.
Ideally, you license the image to them (the record company?) for each specific use, but record companies tend to want the whole enchilada because the image becomes part of the product (the "key art"), and they not only don't want to have to come back and renegotiate with you for additional uses, they may also not want you to use it elsewhere. The question is, do YOU want to use it elsewhere? Its a nice piece of art, but where else would you use it? You might be able to sell prints in an art gallery, or for advertising, or editorial or stock (if you decide to get into that), I think it would sell really well. Do you want to give that up for the flat fee the client will give you? Do you have a choice at this point?
Generally, photographers don't get a royalty from albums (CD covers) so you cut the best deal you can. If the group is loyal to you, and as you rise in the business, you can cut a better deal, which might include holding on to some non-record rights. Don't get me wrong, I'm not advocating giving up your other rights, it just sounds like you already agreed to it, and you don't have the clout to say no at this point (unless you want to walk away from the deal). If the designer is really your friend, ask him how this normally works, but be prepared to not like the answer. Music photographers (like movie stills photographers) occupy a very low rung on the production ladder, and since the images are tied to the album and the artists in it, its hard to seperate out other uses (like how would you get Faith Hill to sign a general model release?).
The best way you can do this is to license the client exclusive rights in perpetuity, but retain the copyright yourself as a matter of principal, and in case you need to sue a third party for infringement (a use unrelated to the album or the artist). For example, you could license the rights to the client (the record company) only, for uses related to the album, with no re-licensing to third parties. That way, you don't put them in the stock photo business (what happens if the the group doesn't take off, and someone decides to sell the photos as an asset to be harvested?). Maybe say that if the images are not used, or the the group dies, the rights revert to you.
You can basically put all this language into a standard invoice. Something like:
"Perpetual and exclusive rights granted to XYZ Music for use on and promotion of, album "Name Here", and all related purposes of said album only. No re-licensing to unrelated or third parties. License transfers upon receipt of payment in full by photographer." (*That's so you can sue them for copyright infringement if you don't get paid, even if they pay the designer who is supposed to pay you, but doesn't).
Put the amount due on the page and that's about all you need. Keep it simple and it will be harder to have problems later. You might also consider hiring a lawyer who knows licensing to advise you and on your invoice language. And be sure to register the images with the Copyright office ASAP - before they get published, unless you decided to give them everything anyway.
One more thing. If they're a reasonably sized company, be prepared to receive a contract from them. Don't be intimidated, just make sure it agrees with your terms and if it doesn't don't sign, or cross out what you don't like, and initial it. Companies like this always ASK for the moon, when all they NEED is a slice of the cheese, and often the contracts while intimidating are just easy when you break them down bit by bit. Don't let them make you indemnify them for anything THEY do. (For example, if you'd hired a model, and they used PS to remove her clothes or embarrass her, and she sued, make sure they don't have language in the contract that says you'll accept the responsibility for whatever they did).
I would also suggest, if you're going to get into this more often, you join a professional organization like APA, ASMP, and/or EP, and read some of the resources I've posted below. That's what they exist for.
(find the short form VAS)
Andy Pearlman Studio