How to Change Store Favicon
If you want to change the Store favicon, replace favicon.png in <APPM_HOME>/repository/deployment/server/jaggeryapps/store/themes/store/libs/theme-wso2_1.0/images by the logo you want to have.
Then, Store will be like below. You will see the new favicon.
How to Change Webapp Favicons
If you want to change the favicon of all webapps, you need to do some code changes. Here's how to do it.
1. Clone wso2 carbon-mediation code from here. Make you sure to use correct branch as per your App Manager version. For example, you need to get release-4.6.1 version for App Manager 1.2.0.
2. Go to carbon-mediation/components/mediation-initializer/org.wso2.carbon.mediation.transport.handlers directory.
3. Change the icon location of favicon icon in here like this.
4. Build org.wso2.carbon.mediation.transport.handlers component. Then there will be org.wso2.carbon.mediation.transport.handlers-4.6.1.jar in the target folder.
5. Add org.wso2.carbon.mediation.transport.handlers-4.6.1.jar as a patch to App Manager server. For that, create a directory "patch0900" inside <APPM_HOME>/repository/component/patches/ and copy the jar into it.
6. Restart the server.
Favicon of Gateway response will be displayed as below.