1. First i think the main thing that would make the program a lot better is the ability to use multiple images, its fine being only able to load one image for the effect filters but with texture generation i think that multiple images is a must
2. The option to rename and create/edit folders, if someone used the program alot its a must have feature, for example if someone had 100 filters/textures in the My filter folder they would have to scroll through a load of stuff just to find what they needed each time, if there was the option to rename they could have My stone, My sand, My filters ect and it would make things alot more organized i think.
3. I noticed when in edit mode if you go to move something with connections it will move more than one module at a time, i think this isn't the best way to do it, it would be much better to just move one module at a time as it makes things alot easier to place where you want.
4. I use modular audio programs also as i make music as well as graphics and some of them have the feature to group together modules into a container module and name and save them to a folder which you can then simply drag them onto the schematic when they are needed next, this would be great for storing custom noises and filters ect and would make the process of making textures alot faster.
Thats all i can think of now, hope you like my ideas