The top 3 biggest tables to check are dbo.JobStatus, dbo.BlobStorage, and dbo.EntityChangeLog.
If the Job Status table has grown to excessive proportions, than you can use this link to change up how long the job status histories are kept: http://blogs.technet.com/b/servicemanager/archive/2010/12/07/more-aggressively-grooming-the-jobstatus-and-windowsworkflowtaskjobstatus-tables.aspx
The Blob Storage table is all your file attachments and those can managed through training or altering your data retention settings.
Hi,
Moreover, You could shrink your data and logs via SQL Server Management Studio to reclaim the space.
Hi,
take a look at this article, it gives a good overview of the possible causes and approaches on solving this:
Case of the fast growing SCOM datawarehouse db and logs
http://www.bictt.com/blogs/bictt.php/2014/10/10/case-of-the-fast-growing
Hope this helps.
Regards,