How to improve sales?

I think that the main problem will be size of your catalogue. You need to have more models (maybe at least 30-50). And also the home decor and furniture category is competitive. There could be also slow spring season for selling and it will be better for you in next months.
I had with 50 models also 0 sales for 3 months (from april to june).

In my opinion, you must impress your potential customer both through model complexity/amount of detail, and top tier presentation. Better differentiate your work from others this way, with higher prices and unique models and scenes, than compete versus hundred of similar models by commercial strategies like lowering the prices, for instance. Besides, improve your workflow as much as you can, or change it right away, in order to do more models in a fraction of the time, because quantity is as important as quality here as well. If your main goal is to make profit selling models, focusing in new, more proper modeling, texturing and presentation techniques for achieving what I've stated shouldn't be a problem for you. Moreover, explore other alternatives like printable models, real-time ready versions, new file formats to distribute. It's not easy and could be risky, maybe is not confortable, but you should think about it from time to time.
Good luck.

Dalia Lasaite, the CEO of CGTrader, presents the best practices for selling 3D models, the new Analytics tool for designers and trends in the 3D market. (https://www.youtube.com/watch?v=xI_HpXuPWms)

You definitely need to listen from minute 14 tot the end where she is talking about advantages of the analytics tool.

I think I speak from personal experience when I say this type of sites will hardly generate a large volume of sales if you focus only on the "artistic" field.

If you sell yourself that way you will get sales every 2 years.

Interior decoration and architecture in my opinion has oversaturated the market with free products. And your prices are not competitive enough to catch the eye of a person who can get something free and who really does not use that much.

With more models and more publicity in external pages, you will know your product even more.