i know what you are talking about.
first it's really never a mastering thing that the album sounds consistent. try imagine an album as an mastering engineer with songs from celine dion, metallica and james blunt and try to get them consistent (that wouldn't work)!
so it's up to the arrangement/producing for most of the part and a bit to mixing.
my approach to get consistency is searching for getting some same elements into the songs like the same drum kit, same bass sound, same vocal sound, same reappearing effects, etc. (kick, bass and vocals is the support of every song for me so if they are sounding at least consistent you can do more crazy stuff around them)
next what i normally use to get consistency is just using a few different reverbs. i have one plate, one room and one hall that i use on everything i want to have reverb. plate is usally on snare and vocals, room is on everything i wanna get consistent aside the low elements (so it is normally not on kick or bass but normally on every other not lead part (be sure to cut out the low end on your reverb) as i try to get the spacing of lead parts with delays to don't put that parts further back in the mix), and hall i use to get things really far in the back to get the depth.
also be sure to use the same mics/preamps/amps/stompboxes/etc. on the same elements.
on the arrangement side, try to put some same elements, melodies or even lyrics that show that this is one piece, from other songs into oneanother.
but aside that i wouldn't worry too much about the consistency as the music share a common genre (you can mix pop/rock with funk/rock for example)!
hope that helps!