Choose a simple and plain, solid-colored door mat to customize. You can purchase door mats made from various materials, so choose a door mat material you find suitable and effective in removing dirt and debris from your shoes.
Create a design for your door mat. Design before you start customizing, or you may have to buy another plain door mat and defeat your entire purpose of customizing the mat on your own. Take the measurements for the mat, and employ those measurements to create graphics and text you wish to place on the door mat.
Draw your chosen design onto the door mat using chalk or a fabric pen you can easily erase or wash off if you mess up your drawing or change your mind when you see the design on the mat. Once you finish drawing the design and verify you want to keep your design, you can start to paint the door mat.
Paint the graphics onto the door mat using acrylic paint and stiff artist's brushes. Acrylic dries fast, so you must work slowly and carefully to avoid going out of the lines you drew in the previous step. Apply several layers of the paint to achieve the desired paint colors and prevent the paint from wearing away quickly. Allow the paint to dry for five minutes between each application.
Use stencils and the artist's brush to paint any text onto the door mat. You may want to stencil in the letters with chalk or the fabric pen ahead of time to ensure you have the text centered or positioned as desired.
Allow the paint to dry for an hour before placing the door mat in front of your door for use.