What was the subject matter of early Islamic art?

Early Islamic art is almost exclusively decorative in
nature.  It refers to the work specifically created to adorn the furnishings and walls
of the mosques created for the new Muslim faith which started in the year 622.  There
was some figurative work made for secular purposes or for the purpose of illustrating
Muslim texts.   For the most part, however, artists were discouraged from creating an
image of any living thing because that was seen as something that God alone should
do.

It was acceptable for artists to work figuratively, if
the figures were part of a decorative pattern and not the focus of the whole picture. 
Other than these figurative patterns, there are 3 major trends in the designs of early
Islamic art: calligraphy patterns, vegetal patterns, and geometric
patterns.

Calligraphy patterns were entirely composed of
letters that oftentimes spelled out blessings or the name of the current sultan.  There
are some pieces of early Islamic art in which a written name seems to be the major
subject matter itself, and that name is itself adorned with calligraphic blessing
patterns.

Vegetal patterns were composed of decorative
lines that resemble flora and fauna, vines and
leaves.

Geometric patterns were created by layering
geometric shapes into balanced symmetrical patterns that sometimes resemble flowers or
sunbursts.