When looking for in-game rugs, or CC, for the Sims 4, one major problem I encountered is that I simply do not like the looks of most re-colours. This even includes the rugs in the Paranormal pack, some look okay, but some colour variations just look too monochrome.
Another problem I found was that of unnatural symmetry. This happens when taking a 1/4 or 1/2 of an image and then flipping, or mirroring, it to complete the rest. Sometimes it works, such as with simple geometric designs, but other times, it just reminds me of a really colourful Rorschach test, or more commonly, a kaleidoscope.
How I avoid the Rorschach test, or Kaleidoscope, effect:
Here you can see a prime example of an image that sort of has the feeling of a rather simplified kaleidoscope (image A). It was created by taking a quarter image and flipping it to create 1/2, and then flipping it again to create a whole.
This is certainly a quick, and easy, way to piece together an image, but it absolutely does look better with some images a lot more than with others.
Image B, shows my solution. While it may look off to modern viewers, this is a rug that is actually supposed to have a middle area filled with a design with the elements all facing in the same direction. It lacks strict symmetry but still maintains some balance.
This was done by stripping the border from the center and then rebuilding the border in a way that looked pleasing while keeping it's symmetry. The center was then spliced in, in segments and areas filled in compliment the look.
This is not to say image A is wrong, the idea can create a, non-authentic, but somewhat pleasing pattern, though would suggest rebuilding the middle areas where the images meet to avoid the unnatural look the mirroring creates.
So, I like the rug but want more colours:
One way to do this is to find something already changed, such as what I did with the top right image. I like this as there are a lot of colour changes to the pattern. (you might notice some rather notable changes to the image, this is because I was experimenting with how to rebuild the border and how to break-up the central pattern)
The bottom left image shows the original but with a colour change I directed to just some targeted areas. I like this way of colour changing things far more than in the last example, which simply applies hue, and sometimes saturation, changes to the entire image. The red and grey rug actually looks like a change that may have actually been done, while a complete hue change was actually far less common, probably due to how washed out those tend to look.
If you want to download any of the shows rugs, I do have the original rug, and it's grey counterpart, (along with 3 other rugs) for download here