Thanks for adding those samples.

Here are the AG's 12th to 15th episodes. There's a slight variation of the Victory over a Gym Leader! track, which seems to be just the introductory seconds of the music with some instruments missing. You can borrow the sample from the AG's 8th episode, at 14:03.

http://www.pocketmonsters.net/episodes/288#Music
http://www.pocketmonsters.net/episodes/289#Music
http://www.pocketmonsters.net/episodes/290#Music
http://www.pocketmonsters.net/episodes/291#Music

Added as: 2002-2005(AG)-M12B ジムリーダーに勝利！ Victory over a Gym Leader! http://www.pocketmonsters.net/episodes/284#Music

AG's 16th to 18th episodes.

http://www.pocketmonsters.net/episodes/292#Music
http://www.pocketmonsters.net/episodes/293#Music
http://www.pocketmonsters.net/episodes/294#Music

Unreleased musics:

AG 17: 14:47, a slight variation of the track Enter the Aqua Gang! (Upon hearing Masato's slip, the man starts to run up the stairs)
AG 18: 08:16/13:49, take the sample from 13:49 as it's the longer version, it's a slight variation of the track 2002-2005(AG)-M34 (An Aqua Gang man stares at Hagi.) and (The group finds out that the Aqua Gang agent is the same they met in the episode before.)

AG's 19th to 21th episodes.

http://www.pocketmonsters.net/episodes/295#Music
http://www.pocketmonsters.net/episodes/296#Music
http://www.pocketmonsters.net/episodes/297#Music

Don't forget to do 5th Short's BGM.

I don't really hear anything different in this track at all. The CD version is obviously a lot cleaner audio than the episode's audio but as far as a different variation here, I don't really hear it for this one. It just sounds like the episodes audio is a bit drowned out that's all. I've added it to the database though as '2002-2005(AG)-M34B'.

Well, I'll explain.´For one, the first 2 seconds of the track 2002-2005(AG)-M34 use different instruments, and I hear the other tracks in the episodes practically as they play in the CD version, so it's not like they sound very different when heard in the episodes themselves. Second, starting from the 5th second, you can hear at least one instrument missing, making it a lower-key version of the music. Third, I just checked AG 54's version of the music (at 05:30), and it sounded exactly as the CD version, only having just a tad bit worse audio quality, but I could still recognize all the instruments from the CD version. So it's definitely a "B" version.
Oh... you've already added it :P Thanks for the understanding.

You also put answers for the unreleased tracks that I reported, but I accidentally eliminated it when I was trying to post an answer of my own. Will try to never repeat it again! *feels guilty*

AG's 22th to 24th episodes. The first 300 episodes are complete! That's nearly half of the first 4 generations!

http://www.pocketmonsters.net/episodes/298#Music
http://www.pocketmonsters.net/episodes/299#Music
http://www.pocketmonsters.net/episodes/300#Music

It really seems like AG has a lot of unreleased stuff.

Unreleased music:

AG 24: 18:39, Satoshi and Pikachu sleep alongside Heigani.

AG's 25th to 27th episodes.

http://www.pocketmonsters.net/episodes/301#Music
http://www.pocketmonsters.net/episodes/302#Music
http://www.pocketmonsters.net/episodes/303#Music

AG's 28th to 30th episodes.

http://www.pocketmonsters.net/episodes/304#Music
http://www.pocketmonsters.net/episodes/305#Music
http://www.pocketmonsters.net/episodes/306#Music

Added the track as: Heigani's Crabhammer - http://www.pocketmonsters.net/cd/view/375#Track-4448

AG's 31st to 33rd episodes.

http://www.pocketmonsters.net/episodes/307#Music
http://www.pocketmonsters.net/episodes/308#Music
http://www.pocketmonsters.net/episodes/309#Music

Unreleased music:

AG 33 - "B" version of the "Contest!" music, at 01:29 (The group arrives at Kaina City, where Haruka's first contest will be held.). It actually played earlier, in AG13, but I didn't notice it at the time. It should be noted that the part that creates the variation only kicks in at 01:41, where some instruments are missing.