Call for Artists, Making Money at Juried Art Fairs, Craft Shows and Festivals
It all depends on the show... and the demographics and tastes of the attendees. There's no one true, universal answer.
Also difficult to advise when you don't mention your medium. Wall art could be photography, charcoal, oil, acrylic, pen, pastel, silverpoint...etc. the list is almost endless. Yet you state you could make small home decor items. Are you looking for advice on that or Art?
I would be more concerned about what your medium is, what your passion drives you to create. Then and only after that would you try to figure out what sizes, styles etc, are most marketable. If you work in the opposite direction you will find it very difficult to make it in this field.
Create work that you enjoy creating and explore your medium and subject until you find a formula that makes you happy and earns you money. There is no answer to your specific questions because everyone is different.