1: The work folder (normally $HOME/Paintstorm) should either be hidden ($HOME/.paintstorm) or in a hidden subfolder ($HOME/.local/share/paintstorm), both are common practice, because cluttering the home folder with unhidden files is undesirable for most users.
2: The .run install script should create a symlink: /usr/bin/paintstorm linked to /usr/share/paintstorm/Paintstorm. This will allow paintstorm to be launched with a terminal command.
3: The .run installer only officially supports ubuntu, however not every user will be using ubuntu, and when paintstorm becomes a bit more popular it is likely that linux distributions will want to create an official package for paintstorm, this cannot be done with a run file. Adding a tarball (just udmp the binaries in a .tar.gz) download alternative to the .run installer would solve this issue and make it easy to create and maintain a paintstorm package on linux for any distro.
4: A common problem for people using paintstorm is that they do not have the GLEW version required by paintstorm (GLEW1.13) but a newer one; so when paintstorm searches for libGLEW.so.1.13 it fails, and by extension fails to launch. I have observed that symlinking it to libGLEW.so.2.1 works as a workaround, but making the software officially support glew 2 and up would be nice.
5: The Linux version currently reports CTRL as CMD, a leftover from the mac version I imagine. It should be labeled CTRL or Control like on Windows instead.
6: Adding support libinput and evdev. Non-wacom tablets will usually work through either the libinput or evdev drivers. There is tablet support available from Qt and GTK, since you are already using GTK for something, adding support for non-wacom tablets through GTK should be an option, albeit probably harder than the rest of the items in this list, but this is definitely also the most important item in the list.
There you have it, a bunch of low hanging fruit
