Extending upon the Unofficial Developer Guidelines, there are a few more things developers should consider in order to create high-quality add-ons for TeamSpeak.

Work as a Team

Open Source projects live on GitHub. It provides a platform for organizing your code and collecting feedback in the form of bug reports and feature requests.

Also, putting your code under an open-source license helps to increase trust in your add-on as everybody can review the source code and suggest improvements rather than having to rely on a black box that may or may not contain exploitable design flaws. Using GitHub's permission system, you can still decide who gets to write to your repository and who doesn't.

Provide Screenshots

The first thing a TeamSpeak user will see when they find your add-on is the first screenshot you upload. Therefore, you should ensure that this screenshot represents your add-on as best as possible.

Screenshots will be scaled to a maximum of 360 x 203 pixels when displayed on the myTeamSpeak website so you should ensure that your screenshot looks good in that size.

In case of an icon pack, you should arrange a selection of your icons so that the user gets an impression of what the most commonly seen icons will look like. This should include at least some of the icons that are commonly found in the main toolbar.

Automate the Packaging Process

While you can certainly create the package file by hand for every new version, it is much more convenient to automate that process in some way. This could either be done via local scripting such as Linux shell scripts or Windows batch files which live inside your repository or via more sophisticated technologies such as Jenkins or comparable continuous integration solutions.

Once you spent the time setting up some automation, you'll never want to do it manually again.

Test your Add-on

It's usually a good idea to collect user feedback before submitting a new add-on version for review. What works on your computer might not work on others.

TeamSpeak runs on different operating systems and a variety of different hardware. Especially themes and icon packs may look ugly in case they were not specifically designed to support high definition displays such as those commonly found in Apple devices.

GitHub allows you to upload pre-release versions which you can use for public testing of your add-on before you submit the next stable version to myTeamSpeak.