Hi Hari,
If you are using CRM on premise, you can navigate to the following folder and change the favicon.ico image;
C:\Program Files\Microsoft Dynamics CRM\CRMWeb
This is not a supported change, and you will likely need to change the favicon again after every upgrade of CRM.
Unfortunately this does not change the favicon for the ADFS login screen if your deployment is IFD.
I haven't heard any word of Microsoft including favicon changing, but with their updates to allow theme customizations we can hope that more branding options become available!
~ Nathan