How to improve on the appearance of a purchased character asset?

Forgive the newb question, but is it possible to improve the appearance of a purchased asset? I bought a character set about a year ago and while the model concept is great for my hobby project, the appearance is just awful. The characters look like plastic (for lack of a better word) with little detail. So it looks rather garish in a scene where much of the art consist of Manufactura K4 and 3DForge.

I am not a graphic artist as much as I wish I was, but apart from using other character assets, is there a way to make models look better? I tried playing with the standard and a few custom shaders, but it did not help much. The asset creator has made no updates with the pack for over a year so I am not thinking that he will upgrade or improve on what was released.

https://www.assetstore.unity3d.com/en/#!/content/14415 is the link to the asset I would like to do something with. The screenshots look a lot better than what the models appear as in Unity 5

Can anyone recommend either specific shaders, or other creative options that would help?

 

Maybe try changing the smoothing angle of the imported models. You can find that in the settings for the model.

 

Mixing and matching environments and models from the Asset Store generally don't yield good results out of the box.

Most of Manufactura K4's environments are not very cartoony vs the animal models. I may be able to give better opinions if you can tell what kind of environments you are putting the animals in.

But generally, if I have a pre-made model (textured and low-poly) that I need to fit in an environment of a different style. I'll bring the base mesh in ZBrush, sculpt in new details, bake out the new maps, and fine-tune in either substance designer or DDO.

 

Agree with Creepgin about the contrasting styles.
The asset pointed to is actually some pretty nice (low-poly) characters. The maps looks nice and the edge flow is good, from just checking them out. I've never used them.
If you are competent in Unity you should be able to set up a shader that brings the character assets to a more acceptable quality level to match the environment quality. But remember those character assets were created before Unity 5 so the textures aren't set up for the new lighting environment.
If I had to update those assets for my personal project - I'd do the same Creepgin suggested, and set up the new textures for PBR.