Hi, I am also no expert but here is what I would suggest:
- Improve modeling like jjaguarbeastproduction already said and also materials (in the description you write realistic material but it's a bit overrated I would say)
- Make also more complex model - Since most of your models are not very complex most people might think they could do that model quickly by themselfs.
- Lower the price for very simple models or put them in a collection (like stool and chair)