- -some basic filter nodes like RGB-curves, saturation/bright/contrast, bluor-filter...
-There is a difference between exporting/importing an image and saving/loading a file and there shouldt be a difference in your program, too. -> when i want to open an image, all layers disappear, because it's like opening a project.
-overdo the brush-saving-system. My idea: the brushes, you used during your workflow are automatically saved within you project files (so any change to the default-brushes shouldt be saved as well) And you shouldt be able to add new default brushes, wich will appear in each project, automatically. But once they were changed in one project, they shouldt remain changed in this particular project. (Mabye, you shouldt think of a back-to-default-option, too.)
-the image-based-color-brushes shouldt "ignore" invisible parts of the image (so try to work with the alpha-channel somehow, because corently, the edges get a little bit messy.
=a smear- and a soften-brush as one of the default-brushes.
=support for tiled images (Importing and drawing...)
http://betalars3d.blogspot.de/2014/09/black-ink-first-conceot-art.html
(The time was limited, because i used the demo-version ... i will defenetely buy the full version, soon! But i usually wait some days so i can think, if i really want a software/hardware)