If you want to add some wow to your art pieces then thread painting is a skill you should master. The only "rule" is you need a non woven stabilizer. Most shops carry this and if you ask the help, they will steer you to the right product.
So this little piece is how I "painted" a leaf in a current piece. The veins are stitched first a reference. Then each colour is stitched in. I usually start with the lighter shades first. Threads over lap. This is what blends them. And I finish all my pieces with a satin stitched edging. I find it crisps up the work.
I think embroidery threads are a must. they add a sheen and stand up to the needle work. How could you not produce something lovely when your threads have names like Orange Meringue, Golden Harvest, Cream Yellow and Deep Gold. Enjoy!