I have used a hangouts-like video conference program with Paint Shop Pro to run a game online, and I have been in a game where the DM used the same setup but used photoshop, so it can be done. That’s how I started before using Roll20. I have also tested the setup with GIMP. And it totally works.
But there are three issues/considerations:
- If you use photoshop, it’s a crazy resource hog, plus video conferencing, plus screen sharing. Lag could be a big deal. The DM who used photoshop had a crazy powerful PC though, so he could pull it off, but even he was concerned about it all the time.
- If you use a drawing or graphics program, be aware that the players can’t move their own tokens, and you lose the ping and other features that make Roll20 so slick. So, if you don’t mind players having to tell you approximately where they want to move every play, go for it.
- One of the drawbacks is that even though as the DM you can have assets hidden in layers, players can generally still see you as the DM manipulating the layer panel, so they can be tipped off regarding what you are planning. Also, if you have a ton of assets on different layers (the players and map alone are five or six), you can have a hard time as a DM finding what you need.
Frankly, it’s enough of a pain, that’s it’s worth jsut learning Roll20 and having your life be way easier. The learning curve for Roll20 appears steep at first, but it’s actually pretty easy once you get into it and just get familiar. Here is the best video I have found on how to use Roll20.
If you want my frank advice, just suck it up, get over that small learning curve, and use Roll20 instead.