So by now a good deal of you will be familiar with the incomplete Season 5 cast poster:

MLP Season Five Character poster

I doubt we're going to be seeing the complete version of this until after the season finishes, so I'm going to be, where possible, 'revealing' the missing characters from the poster using the magic of Photoshop.

Starting with S05E14 Canterlot Boutique: Sassy Saddles, Goth Pony and Bright Pony!
FANMADE S05E14 S5 Cast poster

S05E15 Rarity Investigates!: Wind Rider! (With due gratitude to Mughees in the comments section for pointing out my blindness.)
FANMADE S05E15 S5 Cast poster
Not a perfect fit, but there are actually surprisingly few shots of Wind Rider in the episode where he's not either at the wrong angle or not holding that buffet plate in front of him.

S05E16 Made in Manehattan: Coco Pommel and the Method Mares!
FANMADE S05E16 S5 Cast poster
This one ran into the other chief problem this project has - pose availability. I'm taking screenshots from the episodes and masking the correct poses in. This is entirely reliant on the poster poses actually being in the episode, where in this case, there is no 3/4 shot of Method Mare 1 (the big guy) wearing his trench coat, not even mentioning the fact that he's always wearing his sunglasses with his trench coat. The other three were only hampered by each other and the hill they're standing behind.

S05E17 Brotherhooves Social: Big McInt- er... Orchard Blossom!
FANMADE S05E17 S5 Cast poster

Full size update for S05E18 Crusaders of the Lost Mark: The Cutie Mark Crusaders and three of their schoolmates!
FANMADE S05E18 S5 Cast poster
There was no properly-angled shot of the filly with extensions, and the Crusaders look all blurry because they were cropped out of the photograph at the end, but it's all good!

S05E19 The One Where Pinkie Pie Knows: The wacky waving inflatable hoof-flailing tube pony, and a review of a slightly older character, Incidental Pony/Whoa Nelly! (With credit to MysteriousBrony in the comments for working the latter out.)
FANMADE S05E19 S5 Cast poster
Shape of the silhouette between Whoa Nelly and Sassy Saddles is entirely speculation. But in other news, I nailed the frame for the inflatable.

S05E20 Hearthbreakers: Pinkie Pie's family!
FANMADE S05E20 S5 Cast poster
For characters we pretty much knew where they were going to be, it took a surprising amount of work to get them locked in. Marble was ok, her shot appeared in-show no problem. For Igneous Rock and Cloudy Quartz, their poses in the poster are pretty much their poses in the doorway, except both individually flipped and Igneous's hat flipped back. Limestone never appears in this front/3/4 pose with her hoof raised, so her leg's been spliced in from a completely different shot. Still works.

S05E21 Scare Master: ...Nopony.
Yup. No new additions this episode. I did say I'd be reviewing a couple of ponies, and though I haven't actually committed any ponies from older episodes into the final thing, here are some notes.
FANMADE S5 Cast poster working

S05E22 What About Discord?: No update.

S05E23 The Hooffields and McColts: The, uh, Hooffields and McColts.
FANMADE S05E23 S5 Cast poster
As explained in the comments below, it's basically impossible to lock in these guys to a good degree of accuracy because half of them don't appear front-on in the episode, and the original poster was so low resolution most of the detail is missing by the time the screenshots are shrunk down enough anyway. So, for two McColts and five Hooffields I've just had to stick up a cropped thumbnail rather than try to crop them in.

The Finished Product

From S05E24 The Mane Attraction, plus some revisits to older episodes, brings us Coloratura, Svengallop, Spoiled Rich, Fashion Plate, and Starlight Glimmer, revealing the final character roster!
FANMADE complete S5 Cast poster
So this is it, the final image. Adding in Fashion Plate and Spoiled Rich from previous episodes, since I missed them the first time around; of course Coloratura and Svengallop from the current episode (though Svengallop's expression is wrong; in the official version he'll have an angrier expression) and popping all the way back to The Cutie Map for a clip of Starlight Glimmer that fits. This is as complete as it's ever going to be until the official version is released.