I recently launched a simple charting plugin for WordPress called RJ Quickcharts. During the process I needed to figure out how to add a banner image. The process is really simple but I thought it would have been nice to have a template that was the right dimensions and had the title of the plugin in the right area.
The zip contains 2 files: a 772x250px PSD and a 1544x500px PSD for hi-dpi screens. To use them, simply create your image and save the files as “banner-772×250.png” or “banner-1544×500.png”. The PSD’s already use this nomenclature so you should be able to simply “Save as…” -> PNG. Once saved, move them to your /assets folder in your SVN repo.
Download the Banner Templates Here.
Some links I found helpful while getting these images set up.
History of the banner images and where to save screenshot images as well.
Getting started submitting your plugin
The form you need to fill out to actually submit your WordPress plugin