The wyvern problem is not because of you, apparently it's because of a bug that affected the hoburg hawk riders earlier too. I fixed it any from next version on it should look fine. The wyvern, however, probably needs an overlay to not look silly (you'll probably see once it's fixed and use big shield and big weapon). If you really want to get this fixed quick, go to races/human/poses.txt and add the line:
#renderorder "shadow cloakb mount basesprite shirt legs armor cloakf bonusweapon weapon offhandw hands hair helmet offhanda overlay"
to both mounted poses, ie after the #newpose line obviously.
In general, good job. They look good and seem to be positioned correctly too. Your item definition code looks good and it DOES add the bite attack when I tested it. Your unit has #weapon 352 which is the boar #nostr gore attack, so maybe you did some mistake? The unit price is lower than supposed probably because it's naked and gets the -30% cost reduction and is rounded to closest 5 afterwards.
Code:
#newmonster 0
#name "Unnamed"
#spr1 ".unit_0_a.tga"
#spr2 ".unit_0_b.tga"
#descr "No description"
#gcost 30
#ap 18
#mapmove 2
#mor 10
#mr 10
#hp 10
#str 10
#att 10
#def 10
#prec 10
#enc 3
#size 3
#mounted
#weapon 322
#ressize 2
#end
This is also adding these items to unitgen. With your files occasionally it would indeed generate units with those mounts. I forgot to mention that at the moment you can use #skipchance 0-100 to make mounts rarer. #skipchance 100 means it will never be generated, #skipchance 50 makes it a 50% chance to skip over the mount. This system will change eventually if I can be arsed to code though, since everything else uses a system where you write the chances differently and it's a better system.
You'll also probably want to use the #theme "animal serpent" correctly (and pretty much all the possible minimum and maximum armor things too), ie #theme "animal tiger" for tiger, otherwise you'd see tigers bundled with serpents very often. You'll also probably want to add a claw attack to the tigers since I think they have both claw and bite in Dom3.
I don't care which forum you post on, but I do prefer code tags instead of whole files since that way I can just copy paste the new stuff without worrying it replaces something I've changed recently.