But I wish they'd use the image on the vinyl gatefold as the cover instead (Eddie holding the heart with the Mayan backdrop).
I disagree. I think the minimalistic approach to the album cover works very well, because it creates an air of mystery that suits the album as a whole very well. It virtually invites you to open the cover and listen to the album to find out what it's all about.
Having said that, the whole TBOS cycle has produced some immensely good artwork, including the sleeve mentioned by Mosh. Although there have been some good (AMOLAD, BNW, NPFTD) and great (FOTD) covers as well, there has not been a general art concept this good since SSOASS. By this, I mean a basic visual motif that is followed through on album and single covers, tour posters and so forth. TXF has something like that and is quite consistent, and it gets the atmosphere alright, but I'm not overly fond of the motif itself.