What is it called when you draw a picture of an object and use only the letters found in that name to picture?

There isn't a specific term for drawing a picture using only the letters of the object's name. However, you could describe it as:

* Letter-based illustration

* Typographic art (if the focus is on the aesthetic arrangement of the letters)

* Name-based art

* Letter-form drawing

* Word-picture

You could also use a more playful name like:

* Letterland

* Name-scape

* Alphabet art

Ultimately, the best description depends on the specific style and purpose of your artwork.