Question Regarding Album Artwork

[teahound.livejournal.com]

So I'm in a position right now where I rather desperately need commissions, and accepted one from a commissioner who wanted a transparent background. I said that was ok, and we sorted out details of the commission.

Turns out it might be used for album art - is this something I should have charged extra for? Their userpage lists them as 14 so I'm not entirely concerned that I'll lose out on money if I should have charged more, but I figured I'd ask in case this came up in the future.

Thanks in advance!