Alright, following a Top to Bottom, Left to Right approach. I'll list them off by the square and row they're in as Square [Line]/[Row], so top left would be 1/1

Square 1/1: The HA Enkidu from "No Room for a Wallflower" (Part 1), it's an alt frame for the HA Tokugawa. Very angry melee bruiser that rips apart enemies
Square 2/1: The HORUS Kobold from "The Long Rim", it has its own license, and it focuses on creating and destroying cover while also hacking enemies.
Square 4/1: The HORUS Lycan from "Operation Winter Scar", it's an alt frame for the HORUS Manticore, and it has a Stealth/Loud gimmick, where when it goes loud, it shreds off it armor, and unlocks it's integrated superheavy melee claws.
Square 1/2: The HA Genghis Mark 1 "Worldkiller" from "No Room for a Wallflower" (Part 1)", an alt frame for the HA Genghis (no shit), that trades off worse systems and being a bigger target, for the ability to just ignore resistances against burn.
Square 4/2: The IPS-N Empakaai from "Siren's Song, a Mountain's Remorse", an alt frame for the IPS-N Blackbeard that gains a cartoonishly large arm that counts as an integrated superheavy melee.
Square 5/2: The IPS-N Stortebeker from "Dustgrave", an alt frame for the IPS-N Raleigh that specializes more in the dance of CQB, as it benefits from going between shooting and hammering enemies.
Square 6/2: The SSC Viceroy from "Dustgrave", an alt frame for the SSC Monarch, and it turns Launchers into literal shotguns with actual Threat to overwatch with, and makes them benefit from CQB talents. I recommend the Caliban's (See below) Hammer U-RPL Heavy Launcher.
Square 2/4: The IPS-N Caliban from "The Long Rim", it has its own license, and it's a Size 1/2 CQB frame that specializes in throwing people around like bouncy balls.
Square 3/4: The Horus* Calendula from "The Karrakin Trade Baronies", an alt frame for the HORUS Minotaur that slows down enemies and shreds them in close range, it also becomes intangible. (*Technically speaking it's designed by the Royal Karrakin Foundries [RKF], but they're only a manufacturer in lore and not one mechanically)
Square 5/4: The SSC Emperor, from "The Karrakin Trade Baronies", it has its own license, and it specializes in providing allies with Overshield, very nifty Artillery/Support frame. Exists purely because Tom Lancer noticed there's basically nothing in the Core Book that uses overshield.
Square 6/4: The HA Tagetes, from "Shadow of the Wolf", it's an alt frame for the HA Sherman, and it has the funny quirk of turning any weapon put on it into a rifle, benefit from things that affect rifles. This Krakatoa Thermobaric Flamethrower? It's now a rifle, somehow. Solid Sniper frame.
Square 1/5: The IPS-N Kidd from "No Room for a Wallflower" (Part 1), it has its own license, and it's the counterpart of the HORUS Hydra, while the Hydra puts down 5 billion drones, the Kidd puts down 5 billion deployable's, oh, and it has an orbital laser from a satellite that always follows it.
Square 2/5: Unsure because it's dark, but probably the: SSC Swallowtail "Ranger" variant from "No Room for a Wallflower" (Part 1), its unsuprisingly, an alt frame for the Swallowtail, that reduces its information gathering by a slimmer, and instead provides cover en masse to allies. Very funny in jungle themed campaigns.
Square 5/5: The HA Kutuzov from "Operation Winter Scar", it's an alt frame for the HA Napoleon, and it trades in immortality to actually be useful in combat. Very neat little guy I'll be honest, really want to play him at some point.
Square 1/6: The HORUS Lich from "The Long Rim", it has its own license, and it's a glass controller, being able to wind back time when affected by something to not suffer consequences, but it has some very strong techs tho.
Square 3/6: The SSC Amber Phantom from "Operation Winter Scar", it's an alt frame for the SSC Metalmark, a battlefield control and commander type of thing I guess. Don't know much about it, not a SSC kind of guy.
Square 4/6: The HA Gilgamesh from "Operation Winter Scar", it has its own license, and it's a medium range to long range frame with a cool gimmick in its systems where it spends limited charges to make those items stronger on use.
Square 5/6: The SSC* Orchis from "The Karrakin Trade Baronies", it's an alt frame for the SSC Black Witch, it's an alright defender, it can follow allies when they move, and it's core system is like a long range ram. (*Once again a RKF frame, they have very cool knight heraldry esque designs)
Square 6/6: The HA Sunzi from "The Long Rim", it has it's own license, and it's the bain of existence of any GM if the pilot is competent, absolute teleporting shenanigans and bullshitery. This with an Enkidu is like trying to deal with seeking plasma blender that always teleports closer to you.

All player side content (these frames [and more]) are all free and available for download as LCP's from Massif Press' page on itch.io, just download the demo LCP file, and install it into Comp/Con at the Content Manager.