There are quite a few UI objects that let you upload your own images, if you create these in illustrator you can easily customise the look of your applications. Have a look at the helpfiles for [fpic] for background images, [pictctrl] for buttons, [pictslider] for sliders and [matrixctrl] for grid-like controller and dials (with the dial mode attribute). There's also [lcd] and [jsui] if you want to script your own. I've heard a lot of talk about knobman for automatically creating images but have never used it myself, it might be worth a look.

maybe I should be more specific. I want to create interactive projects, so interface interacts with interface via video or something along those lines.

Im not sure if I understand what you want to do Lukasz but when I started using Jitter I found it really helpful just to try different patches and when I didnt understand what an object was doing I just unlocked the patch and rightclicked on the object and looked at the helpfile for each object

In Jitter Recapies 1,2 and 3 you find a bunch of sample patches to start with

https://cycling74.com/tutorials/jitter-recipes-book-3/

I want to affect objects on a screen (made in illustrator/photoshop) and have them do things like you would on an user interface. it can involve a camera on the person maybe even more like: http://www.k2.t.u-tokyo.ac.jp/members/alvaro/Khronos/Khronos_Projector.html#InstallationSetup

I just don't know where to start. It's all very overwhelming. I will try that link though :)