Here are some other materials to help enhance your list of art materials:
Glue - Whether it is sticks or the liquid kind, those name brands, such as Elmer's, seem to work the best. Other brands can serve a purpose, but don't last as long.
Stencils - Children can refine writing skills when tracing along the outside of a stencil. They also help them to practice drawing skills. Cardboard stencils wear out faster than plastic ones, but you can laminate the cardboard ones for more durability.
Stamps and Stamp Pads - You can buy small wooden stamps at art supply stores, or larger ones with handles, designed for younger children, through school catalogs. Children love to stamp and can embellish prints with drawings. Also, use materials found around the house or classroom for different stamping experiences. When purchasing stamp pads, look for ones that have a secure lid to avoid drying out, and nontoxic ink.
Play-Doh - Play-Doh and clay provide three-dimensional exploration, while also refining fine motor control. Collect different kinds of tools, such as rolling pins, cutters, cookie cutters, and more, as well as experimenting with different types of Play-Doh and clay.
Colored Pasta - Purchase pre-colored pasta, or make your own by soaking pasta in rubbing alcohol plus food coloring. Use different varieties for different stringing experiences, whether on yarn, string, or pipe cleaners (chenille sticks).
Collage Items - The collage tray can be one of the greatest open-ended art projects in preschool. Anything that children can glue can be kept in the tray. Use paper roll tubes, feathers, craft sticks, chenille sticks (pipe cleaners), tissue paper, straws, yarn, felt, foam pieces, magazine photos, buttons, rice, pasta, etc.
Works of Art - Display famous works of art, through posted prints, matching activities, and books, to expose children to the Greats. Perhaps they will be inspired to emulate the Masters.
Aprons - Aprons are necessary to keep clothing clean. Use either commercial plastic ones or old adult shirts that are worn backwards.
Clean-up Materials - Children need to clean-up when they are finished. Provide a child-sized broom, dustpan, and plenty of soap and water. Demonstrate how to use them accordingly.