Progress:
Templates for white, blue, black, red, and green army cards have been made in GIMP 2 with default text fields and formatting. This will expedite the process of adding the stats from the original Heroscape units' cards to ones matching the layout of AotP army cards. It will also keep army cards consistent, and will hopefully allow players with physical Heroscape sets to print out the new army cards for use at home. I will also make sure to export cards as .png files so they will not artifact over time, though this will increase their file size (although with their relatively small resolutions, this should make little difference).
Setbacks:
Card scans from Heroscapers are unfortunately low in resolution, and having been all exported as .jpeg files, they have some artifacting that makes enlarging the cards look extremely ugly. Without resolving this, the card portraits and hitboxes will be a pixelated mess. I attempted manually fixing Syvarris's hitbox in GIMP, but made no real impact in the process.
Solutions:
Another mod for Tabletop Simulator has HD scans of the official Heroscape cards. My plan is to install this mod and attempt to extract the images so that I can progress.
I also may look into using MSE (Magic Set Editor) after confirming that I can make these cards at all. It seems that Heroscape templates were able to be imported to MSE to make new cards. If I could do the same with AotP and the card templates I have, this may help speed up the process even further.
I will update as soon as I have either completed the Rise of the Valkyrie set (as much as I can, anyway) or have other significant news to report.
EDIT: Well, I figured out how to get those scans...Take a peek at the madness behind my method[pbs.twimg.com]

Progress:
First off, I have made my own army card templates using official high-quality images of the army cards from Battle For Zendikar. These templates include purple colorless (for Eldrazi and artifact creatures) and gold multi-colored (not sure if I'll actually use it, but it's there). I have also made a Tumblr blog for posting the cards to. You can find the blog here[aotpheroscapeproject.tumblr.com]. There is a Card Archive hyperlinked in the description. I'm going to see if there are any Tumblr themes available that still support "pages" to make this easier. I have also released Syvarris, Ne-Gok-Sa, Marro Warriors, Sgt. Drake Alexander, Airborne Elite, Agent Carr, and Krav Maga Agents. This makes 7 of the 16 army cards from Rise of the Valkyrie already complete.
Setbacks:
Having just gotten a job, and with college starting back up, my time to work on this project is limited. Work will happen whenever I have time, so expect slow progress until I have my routine set.

Keep up the good work, we all know it's not easy to contribute to a mod and also having to deal with real life issues.

Thanks for understanding! I actually haven't checked my notifications until now (oops). Here's hoping the project continues to go smoothly. I'm thinking I'm going to work on either the vikings or Grimnak and Mimring next, with the other following immediately after. If anyone has suggestions for how certain units should be converted (color, sub-ttpe, ability balances, etc.), feel free to comment on this thread or send an ask to the Tumblr. I'm going to make sure Anonymous asks are turned on there, so you won't need an account to do so.