Welcome to the fun! I just embarked on the same project at the start of the year!
Shadow is based on Major, so if you have unique 3-digit major images they can work in Shadow, with a couple caveats.
You need to make sure the 000-099 words do NOT have s-consonant blends to start, so nothing like SLiMer or STaN, because some of the court-card combos use these S-blends and they will conflict. Also, try to avoid words that start with H sounds, as some of the King pairs start specifically with H’s.
The original post by Lance lays it out, but it does take a few read-throughs to really sink in.
@BradenExplosion is incredibly skilled with Shadow and has written quite a few awesome posts about it. It’d be worth browsing through his contributions for sure.
I also made a couple resources to help with building Shadow words out, check out this post, it has a link to a Google sheets file with a re-worded explanation of the system, along with blank grids that show every card pair and their phonetics:
Lastly, I’ve also shared a zip file with small images of all 2704 card pairs to make building in Anki easier and more visual. Feel free to use them if you’d like once you’re ready to start associating!
I’ve got a thread going for my project, I’ve found it helpful and motivating to jot down thoughts about the process as I go. Efforts to learn the Shadow System and memorize a deck of cards in under one minute - #44 by TheHumanTim
If you feel up to it, it would be cool to see how you progress, maybe make a thread to document your efforts in the “memory training journals” section of the forum too? I’d love to see how someone else is handling the craziness of learning this along with me!
It is a daunting task, the word building takes a LONG time to make sure they’re unique and vivid, and then you have to associate them to a consisten image and to their appropriate card pairs, which is a whole other process, haha. I’m about 1/3 of the way in to the image association process and it’s going well, but it’s not something that can be rushed, especially if you’re new to the process. (I’ve only been doing memory stuff for a short time as well, about 10 months.)
Best of luck!