why not try to make your own? an artist who creates a large work wouldnt much want to sell it cheap, i'm thinking.

or consider hanging a carved panel, found at asian type furniture stores.

Link to top 10 affordable artists in Toronto, including a students gallery, if you are looking for original artwork. Site is from 2013, so you may want to call a loation first to inquire. http://www.blogto.com/arts/2013/11/the_top_10_places_to_buy_affordable_art_in_toronto/

Mount an interesting piece of fabric, Marimekko, for example. https://us.marimekko.com/fabric/cotton-fabrics

You could also consider a vinyl wall decal. A couple of examples from Etsy that are inexpensive enough to replace when you find the perfect art:

https://www.etsy.com/listing/231948317/birch-tree-wall-decal-nursery-forest?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=vinyl%20wall%20decal%20large&ref=sc_gallery_1&plkey=81bb8cb1db9d30103e82530e02f66251b8b65282:231948317

https://www.etsy.com/listing/62495865/modern-damask-large-tree-vinyl-wall?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=vinyl%20wall%20decal%20large&ref=sr_gallery_14