How to add a custom icon in the Ribbon for outlook custom form region

Icon for custom form region in the Outlook ribbon can be set programmatically as follows:

1. Firstly in Solution Explorer, double click on the .resx file of the form region.
2. Click on Add Resource->Add Existing File option and select the desired icon file through the Browse window. This will add the image file in a separate Resources folder.

3. Navigate to the InitializeManifest() function in the code window of form region file and add the following line:

In the above code, “PageIcon” is the name given to the image while adding it to the .resx file.