when doing a search everyone else is calling it Wall Decals
Doing a quick google search you are competing with Amazon, Fathead and Target all sites that have spend a ton of money on their sites to make sure they get found.
What have you done for yours?
I would add in more text to the home page and add in the wording Decals many times.
Get good backlinks.
Example this site link is on page one for a search for wall stickers.
Wall Stickers, Wall Decals, Wall Appliqués
If you count they have the word sticker or stickers or wall stickers on the home page over 100 times.
That's around 98 times more then your site dose so they will show up 98 times better then your site for a search for wall stickers.
They also have hundreds of more products then you do for sale making the site more seo rich with more content for all the hundreds of products text that is seo done right.
It is going to be hard to compete with all the larger sites just do to the fact that they have so many products all with text making the site very large compared to yours.
You can try running local targeted ad words for some towns that will not cost as much as running a wide open ad word package and go after more local customers on a town to town basic.
Another thing you can do that works is make lots of website for lots of towns like.
Make 50 websites and call each one
townnamewalldecalsstickers.com replace town name with a town name and do this for 50 towns.
Tweak out all the seo for each site just to show up for that town this way you can beat out the big guys with a local targeted site.
Now you have 50 sites that show up great and if you sell 2 items a week from each site you then sold 100 item that week.
Many marketers do it thios way go for low sales number but do it on lots of sites and it ads up fast.
So if you made $20 on each sale and sold 100 in a week you would be making $2000 a week. it just takes a lot of time to get all the sites up but over 6 months to a year you are then doing good.