If you are a programmer and want nice 3D assets for you game, creating them yourself might be easier than you think. Using a 3D modeling software such as Blender, you could quickly learn to make simple but visually attractive things. It just takes a little time to get used to modeling mechanics and some great references to look up to. With that in mind, here's a list of game from which you can draw some inspiration from.
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
Clusertruck by Landfall
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
Monument Valley by Ustwo
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
Crossy Road by Hipster Whale
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Overland by Finji
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
Grow Home by Ubisoft
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
Parkitect by Texel Raptor
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
The Family Farmer by Dpt.
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
Race the Sun by Flippfly