Can I use images uploaded by users on Google Maps to display on my website ? If yes, do I need to reference images back to the Google Maps and how ?
In order for you to legally used images uploaded by Google Maps users on your own site, you meed permission from each user for each photograph for each instance of usage; this is because Google allows each uploader to retain copyright protection for uploads. See the Google TOS below.
The idea that you reference or link to the image at Google Maps makes no difference; a link may be a stipulation of the permission you get to use the image(s), but it in itself is not getting clear written or verbal permission to use copyrighted images on your own site.
This is Google TOS as it pertains to end user materials (my emphasis) :
Your Content in our Services (From Google Terms of Service – Privacy & Terms – Google)>
Some of our Services allow you to upload, submit, store, send or receive content. You retain ownership of any intellectual property rights that you hold in that content. In short, what belongs to you stays yours.
When you upload, submit, store, send or receive content to or through our Services, you give Google (and those we work with) a worldwide license to use, host, store, reproduce, modify, create derivative works (such as those resulting from translations, adaptations or other changes we make so that your content works better with our Services), communicate, publish, publicly perform, publicly display and distribute such content. The rights you grant in this license are for the limited purpose of operating, promoting, and improving our Services, and to develop new ones. This license continues even if you stop using our Services (for example, for a business listing you have added to Google Maps). Some Services may offer you ways to access and remove content that has been provided to that Service. Also, in some of our Services, there are terms or settings that narrow the scope of our use of the content submitted in those Services. Make sure you have the necessary rights to grant us this license for any content that you submit to our Services.
An individual user might demand, as a condition of your use of an uploaded image, attribution in the form of a link back to Google Maps, or in the form of a link to the uploader's own site, or in some other way. If the uploader included with the image a release to others via a specific license, then you can use the image by complying with the specified license, whatever it might be (I am not sure if GM permits uploaders to specify a license for reusers).