Nice, I like the boat in particular. It is difficult to see what settings you have used and as for materials well, it is a bit of alchemy to come up with the right ones. If you want to pick up tips there are a few people who would be able to help besides myself and it would help if you could post a screen shot of your light settings, just select the lighting control on the top of the renditioner window and you will see a small light bulb, Select this and you will get the option to change lighting settings. while this window is open, print the screen and crop and save. We can then get a better insight into what you are trying for. It is helpful if you want to see what others can come up with to attach the model and the .lwx file which is the save folder created by renditioner when you save your settings. I am going to try to get the extra material files attached to the artisan or the renditioner site so you and others can download them but cannot say when I can get it done by. Welcome to the forum and anything you need to ask will be answered to the best of our abilities.
A note on the textures used in those renders above, the boat hull could do with a bit of shine on it, possibly a satin finish and the smokestack in the first render appears to have an obvious tiling to it, I might be wrong there as I do not know the texture.