For this challenge, you will be removing an object from the background. You may follow this tutorial if you need instructions. Then return here to show off your extraction. (By showing your creations, you are inspiring others). Once you have shown your unique creation, you are free to add your creation to your kits.
When I scan an image, I use a higher than 300 dpi scan so I get a sharp image. After I extract it, I adjust the dpi to 300 without changing the image size. This prevents any quality loss.
A few flowers I've done, before and after extraction:
I work with either high-res scans or high-res photos (keeping my camera on high quality where possible). I have an older version of Photoshop without the neat edge-finding tools so I use the Quick Mask tool and my tablet to select the part I'm extracting. The real trick is to make sure to use a large, quality shot with reasonably clear edges (depending on your method of extraction).
Your extractions look to be excellent. You are absolutely correct that high-res scans and high-res photos are the key. If you do not start with high quality image, you cannot create a high quality element.
And before anyone thinks that they need a super-fancy camera for this, I will mention that the first two photos were taken with a Canon PowerShot (decent quality but not DSLR levels), and the rose with the camera and default settings on my Galaxy S7. It's more important that you have decent lighting (indirect, like a cloudy day, unless you really want the harsh shadows) and a steady hand/tripod.