What specific artwork categories are you seeking?
Apple's applications are not Microsoft Office clones, and do not have any equivalence to Microsoft's Smart Art found in Word, Excel, and Powerpoint. Apple's applications have strictly limited shapes, lines, and bezier lines from which to build more advanced artwork.
If you want Smart Art functionality, why not use Word or Powerpoint online, or Office 2016 for Mac, and draw from available Smart Artwork templates?
Jumsoft has free designs (e.g. Toolbox for Numbers, and Keynote) in the OS X App Store, which feature several in-app purchases for infographics, clipart, diagrams, etc. Want quality artwork, you will have to pay to play.
There is the free draw dot io site that has a kazillion diagrams, and the ability to download your finished work to your Mac as PDF, or a variety of image formats.