Its important to know if you need this relief in SolidWorks to produce a mold or other tooling, or if you just want a visual representation. Depending on your SolidWorks version, you might be able to import it as a decal (texture map) and put it on your model in place of the relief.
If you must have the actual relief in your SolidWorks model, it becomes a longer process.
This kind of work is better suited to a polygonal modeling application to create the relief model. You could learn to model relief like this in SolidWorks, but it is usually not cost effective to model as nurbs compared to other methods.
There is 3d art available for purchase from vectorart3d.com and others, but the files are usually triangulated (STL) and would need to be converted to nurbs surfaces in another application in order to use in SolidWorks. This could work for you if you can find a pre made design that works for your application and can get it converted to nurbs.
There is a method for producing a 3d surface for visual reference based on a heightmaps. Companies like gantryco.com sell this kind of art as a greyscale image (heightmap) where the depth is related to the greyscale value. Black is usually the deepest and white the highest.
There is a free application called ZSurf (search Google for a current download location) that will take a heightmap and produce a 3D nurbs file in IGS format. Rhino can do this from a heightmap using the drape function too, and usually produces a better quality surfaces.
Using heightmaps to make a nurbs model generally does not result in good detail or crisp surfaces, but if you really want the 3d representation in SolidWorks, and don't plan on using it for anything other than a reference, it might be an option.