Hi Eerin,
Lovely items! I like your photography and even though you have a variety of items, the shop looks cohesive.
On a listing-by-listing level, though, I think you need to do a little bit of work fleshing out your descriptions and working on titles and tags.
Using the "Butterfly 3, Print" as an example:
"A 9 x 14 cm illustration (print) on 20 x 30 cm good quality paper."
I'd include inches measurements for us slackers on the empirical system. "Good-quality" is subjective and not very detailed, so I'd explain exactly what kind of paper you use, from the label of the paper -- weight, brand, type -- and why you use it.
"The illustration (print) comes without a frame so that shipping is easier. It will be packed in a way that protects the print perfectly. The frame that you see on the 3th picture is just to give an idea of how it would look framed."
I think that "This listing is for the print only -- frame not included" is enough. I'd go into more detail on "will be packed in a way that protects the print perfectly"
"Materials used: copic sketch markers, pencil (graphite)"
I'd move this up and detail more how you make the sketch. Is it freehand? Based off something, or from your mind? Example:
"I hand-drew this one-of-a-kind orange-and-tan butterfly artwork with a graphite pencil, then hand-colored the sketch using non-toxic Copic sketch markers, which deliver high-quality, saturated color and dry 100% acid free." (capitalize Copic since it's a brand-name)
Your title should be optimized for search -- rather than giving your artwork a title there, use search terms that people will plug in and that are repeated in your tags.
"Butterfly Art Print, Pencil Sketch with Orange and Tan Coloring, Butterfly Drawing, Nature Art" or something like that. Then in your tags, have
Butterfly Art
Pencil Sketch
Butterfly Drawing
Nature Art
Looking at your tags, use multiple-word search phrases. You will be lumped in with a million other listings with one-word phrases like "moth, original, wings, pencil.
Do people search for "moth drawing," "copic markers," "eerin vink" or "moth art"? I'd probably sub more-searched phrases for that. If you plug the beginnings of phrases into the Etsy search bar, it will autocomplete based on what people are searching.
Also you can check shops that sell similar items to yours to see what they're using for titles and tags.
It's a huge learning process, this whole SEO thing, but your hard work will pay off! :)