Option 2/B could attract a much wider audience to the game and could lay a foundation for your sequel game in the future. In the process of moving to the new engine, you could add a few token updates - new modifiers, new card set, doesn't necessarily need to be full transformation/class - a few updates would bring people back and make previous players engaged again (assuming they beat the game or saw most of the content in the past). Concerning art, what about a batch workflow to crop all the images and process them through img2img on very low settings? The img2img step to add some faux detail if the problem is a question of resolution on some existing images... much more involved if the source files for the (PS or INDD?) templates no longer exist though.I'm seriously considering doing some new work on TF Card Battle. I've got a couple options and I'd like to know what people would be interested in.
A: Just more content added to the HTML version. The easiest thing but the least interesting to me personally.
B: Porting the game over to the The Monster Within engine. Wouldn't be that much work, although has issues with art. I don't know if people really want that over just playing the HTML version though.
C: Make a full-fledged TF Card Battle 2. This would be very far off, I'm talking years from even starting production. But I could start exploring design space and such if people like the idea.