(Elves)
4x Llanowar Elves - Required by tradition, though if I get enough Elvish Mystics, I'll probably replace these. I won't bother to buy singles, though.
1x Ezuri's Archers - Post Lord of the Rings, you gotta have an elf archer, and this is a good early blocker.
2x Elvish Visionary - Increases card flow and can act as a blocker.
2x Viridian Emissary - I originally had Sylvan Ranger in this slot, but I felt that having another 1/1 creature wouldn't be a good idea. Viridian Emissary is better at both attacking and blocking, and I feel like the death trigger is more satisfying than the ETB trigger. I used the Planechase version that has the "dies" wording.
2x Elvish Archdruid - While all five decks have a tribal component to them, this is the only one to have two lords. This gives the other weaker elves something to do, plus, you know, can really accelerate mana.
(Smaller green creatures)
2x Garruk's Companion - A strong early creature with trample, and notably has just trample with no other abilities, which is a plus in this deck.
2x Centaur Courser - I make sure to have at least two vanilla creatures in each deck, and it's good to have centaurs in this deck.
(Big green creatures)
1x Cudgel Troll - This creature has regeneration with no other abilities, making it easier to explain the ability. Plus, he's a good blocker in a pinch.
2x Garruk's Packleader - While casting big creatures, this allows for smooth card flow.
2x Sentinel Spider - Originally, one of these was Giant Spider, but I realized it didn't feel right for a creature while a mana cost of three or more to not trigger Garruk's Packleader. For each keyword in a deck, I prefer there to be at least one creature that has just that keyword and no others, and while Ezuri's Archers can kind of count for reach, there are no other creatures with vigilance, and this creature has reach in addition to that. However, there aren't any flavorful green creatures with vigilance by itself, and I wanted this creature in this deck, so I decided to make an exception.
2x Stampeding Rhino - This is probably the best possible creature to explain trample with.
1x Soul of the Harvest - Originally I had Yavimaya Wurm in this slot, but for the second most expensive creature in this deck to be 6/4 felt rather underwhelming. Soul of the Harvest not only has higher defense for the same price, but also draws cards. Also, I decided that wurms wouldn't be very familiar, while "kind nature spirit that is very strong" would be more recognizable.
1x Craterhoof Behemoth - I try to include the iconic creature type of each color in that color's deck, but I decided I didn't want any +1/+1 counters or X cost spells in these beginner decks, so that leaves out all hydras that aren't obscenely expensive. "Behemoth" works as a good alternative, and this is a great finisher. It does require explaining haste when there no other haste creatures in this deck (though there is a haste spell), though here it's mainly in the context of "all your creatures attack, you win", so I think it's fine. And yes, when testing against my coworkers' more serious decks, I did hard cast this multiple times and win.
(Boosters)
2x Giant Growth - The original.
2x Savage Surge - Untapping allows for surprise blockers, and in some cases with Elvish Archdruid, it allows for mana acceleration mad techs. I used the Return to Ravnica art, since with the Theros art, it didn't really seem like anything was actually happening.
2x Trollhide - Decent aura, and the name ties into Cudgel Troll.
(Red spells)
2x Fall of the Hammer - Despite all the big creatures, I found that this deck actually does have trouble against other big creatures, creatures with evasion, and creatures that just hang back and don't attack or block. Red can deal with that, of course, but I wanted to have some spells that took advantage of the generally high power of the green creatures, and my experiences in Theros block limited gave me an appreciation of this spell.
1x Act of Treason - This can be a seriously awesome spell to cast at times.
1x Warstorm Surge - Another way to leverage the generally high power of the creatures in this deck, though I often had the experience of only drawing Llanowar Elves and such after casting this, so I'm considering replacing this with that new M15 aura that allows the creature to tap to deal damage equal to its power.
1x Into the Maw of Hell - I originally had Fireball in this slot, but I decided I didn't want any X spells. This is a fairly expensive red spell that the red beginner deck wouldn't want, but it could be reasonably expected to be castable in this deck, and it's an awesome effect.
(Other)
2x Naturalize - Another green mainstay. The inclusion of this in the main deck did warp the other decks a bit, though, in the sense that they all include enchantments and/or artifacts in decent quantities. I used the Gatecrash art; I really don't know why they keep using the gobstopper art, since this is the best one so far.
(Lands)
14x Forest
4x Gruul Guildgate - I felt the need for nonbasic lands, and these are both the simplest and the cheapest.
5x Mountain