Hi there. Arguably the market standard for a render engine is V-Ray. Have a look at their gallery at V-Ray for SketchUp Gallery.. Also Corona Renderer is a great one as well. It’s fairly new but unfortunately their SketchUp plugin is not yet ready. They’re working on it and it’ll be released in 2017. Nonetheless the quality is great. Have a look here.
Also, Thea Renderer, Kerkythea and Indigo Renderer are great as well.
I’d personally go with V-Ray. It has a bit of a learning curve but it’s the best (once again, arguably). Good luck! 
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