Unfortunately I haven’t yet found these readily available around where I live in the UK, but Indi from the States has done all the hard work for me and provided a complete list of the codes for Series 4.
As with Series 3, it looks like the code isn’t the last character in the code stamped under the barcode, but is in fact the letter before this. Sorry I don’t have an image to illustrate, but you can see from the Series 3 page what I mean.
Anyway, on with the codes –
Again, no textual description of the characters, just an image – here’s what Indi has called them and I think these descriptions are as good as any –
A – Slime Cubes B – Tabby Cat C – Screaming Enderman D – Sneaking Creeper E – Zombie at Door F – Spawning Spider G – Rabbit H – Skeleton Archer (with Pumpkin Head) I – Steve? (with Leather Armor/Arrow Damage) J – Priest Villager K – Alex (with Cake) L – Sheared Sheep
Hope this helps!