Hi Prashant,
I believe the snapshot service grabs anything in the current viewport but may not take in environmental transparency. Snapshot with white edges:
You can either use a 3rd party library to crop the photo or use our Asset-Jobs API to create a server-side render of the item. This does take environmental transparency into account. Asset jobs version with transparent background:
Finally, you can also pre-render the items on the platform and retrieve them from our layers service by passing in parameters.
Please let me know if this is helpful!