Lots of wall hangings attract attention. If you have a flower garden, fill vases with fresh cut flowers. Not only will your room smell good, but it is attractive to the eye as well. Throw rugs can improve a rooms appearance as well. Go with contrasting colors for effect.
Most department stores sell small rugs for a few dollars.
Hit garage sales for inexpensive tables and chairs. It does not cost much to refinish a shelf, table or chair and no one will know it is not new. Houseplants not only improve the air quality of your house. They add to the decoration. Check grocery stores with Florist Departments.