One feature I would like to see is the ability to occasionally choose a paid picture to do for free. This could be done in a few different ways. One way would be to replace the daily picture with the chance to choose a paid picture for a day every month or so. With the wide range of tools and palettes, plus the color wheel, and access to every picture right then, there is still a very strong incentive to subscribe. Even with the ability to chose a free picture occasionally I would still subscribe whenever I could afford it. I also believe that the ability to choose a paid picture may help keep newer people playing longer, which then makes them more likely to subscribe.
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