P9 UI is a "What You See Is What You Get" (WYSIWYG) tool for creating ScriptUI interfaces.
It's easy to use, you can move elements around, alter the dimensions, and copy them by dragging your mouse.
When you're finished, you can save your UUI in a folder or click the Code button to obtain the code, which you could just insert into the script.
For images, it converts them to binary strings. This means you don't require dependent files from outside.
