A great place to start is with your item title, description and tags and what buyers use as search terms. There are many tools out there which provide free information on the number of searches people do on google monthly for any particular item (Google adwords keyword planner). Google keywords follows people's search terms in general.
Using google adwords, when I put the two keyword phrases in your title "Moroccan kilim pillow, vintage boho pillow with zipper n.09", into the planner, there were 50 searches/month for moroccan kilim pillow and 0 for the second phrase. It's good to have both detailed and more general keywords in your titles. SEO takes some real studying, but in time, it does start bringing alot of people to your shop...over time!
Here are some ideas for title and keywords with the number of monthly searches on google:
decorative toss pillows - 720
kilim pillow covers - 880
pillow for sofa - 880
pillow covers - 1300
kilim cushions - 1600
sofa pillow covers - 3600
kilim pillows - 5400
Aim for 500-1000 for targeted keywords, and low thousands for more general terms. More targeted keywords get fewer views, but convert to sales more. There are many other ideas besides these. Multi-word keywords are best for tags rather than single words which yield hundreds of pages of results - really hard to get found. There is a team here which really helps demystify SEO. Here's the link and good luck. Your pillows are very bright and cheery and you should do very well with them!
https://www.etsy.com/teams/11352/etsy-seo-google-seo-copy-writing-small