When I write about our art areas I get so many comments from parents not wanting art materials at home because of the mess, 'my kids will dump that all out on the floor'. Like any Montessori areas, we start with the basics and work up to more materials as the child develops and is able to have more responsibility.
This (above and below) is our art area when Otis was a toddler (14 months) and Caspar was 4 years old. You can see Otis could only access the low shelf and this had three activities on it. The easel had been shortened to make it toddler size too. You can see more details here.
This is our art area (below) when Otis was four, you can see more detail on this art area here. The most significant change was having a dedicated art table. This allows the children to do more art, leave it out for longer and for me to be less concerned with mess. This area also had more art materials accessible and a place to hang finished art.
These (below) are our art shelves now Otis is five. There are a lot more materials on the shelves and Otis is able (for the most part) to keep it organized. We still need a clean up every now and then, and we are always rotating and bringing in new materials. At five he has the freedom to do a lot more art activities independently but also the responsibility of maintaining a larger area.
You can see more of this area here.
If you are interested in Montessori classroom art areas you can read a previous post 10 Fantastic Montessori School Art Shelves!