score:22
As a quick note on chronology, "5000+ years ago" would put your setting in the Jemdet Nasr period or earlier (Uruk III–V; yes, archeological periods are numbered backwards).
This is around the time when the earliest forms of "cuneiform" writing first evolved out of pre-literate pictographs used for accounting, and the signs used at the time looked quite different from later cuneiform. In particular, I'm putting the word "cuneiform" in scare quotes here, because this time period actually falls right in the middle of Sumerian writing evolving from a "linear" style to a "cuneiform" style as scribes increasingly simplified the signs, which were originally rather detailed and pictorial line drawings, and started composing them out of wedge-like line segments made by pressing the side of the stylus into clay.
In other words, if you want your temples to feature period-appropriate writing, don't think this:
The upper 1st (top) register, side A, of the Black Obelisk of Shalmaneser III. Neo-Assyrian period, 825 BCE. Photo by Osama Shukir Muhammed Amin FRCP(Glasg) via Wikimedia Commons, used under the CC-By-SA 4.0 license.
but rather something more like this:
Administrative account of barley distribution with cylinder seal impression of a male figure, hunting dogs, and boars. Probably from the city of Uruk. Jemdet-Nasr period, c. 3100–2900 BCE. Photo donated to Wikimedia Commons and dedicated to the public domain by the Metropolitan Museum of Art.
or even like this:
The Blau Monuments. Uruk III / Jemdet Nasr / ED I period, c. 3100–2700 BCE. Illustration by from A history of Sumer and Akkad by L. W. King (1869-1919) published in 1910, now in the public domain.
or this:
The Stele of Ušumgal. ED I–II period, c. 2900–2700 BCE. Photo donated to Wikimedia Commons and dedicated to the public domain by the Metropolitan Museum of Art.
Ps. The Wikipedia links above should take you to a bunch of images of period-appropriate inscriptions and statues. For more images, consider searching museum collections or the CDLI for objects from the appropriate periods. (Note that CDLI doesn't recognize "Jemdet Nasr" as a distinct period, but searching for e.g. "Uruk III" or "ED I-II" gives you objects from c. 5000 years ago.)
Note that most if not all of these statues and reliefs would've originally been painted in bright colors. Most of the pigments have just decayed or rubbed off over the millenia, leaving us with limited evidence of their original colors. For some reconstructions of the original colors in ancient Mesopotamian sculpture, you could take a look at the recent book Mesopotamian Sculpture in Colour (ISBN 978-3-935012-42-3) by Astrid Nunn and Heinrich Piening (eds.) published last year.
One well known example of artwork from this period with (partially) preserved colors is the so-called Standard of Ur, a wooden box with colorful mosaic decorations depicting scenes of warfare and a court banquet. The striking blue and red colors of these scenes have survived, as instead of paint they were made with inlays of lapis lazuli and red limestone respectively. Some boards for the "Royal Game of Ur" with colored inlays have also survived.
The "Standard of Ur" on display in the British Museum. Early Dynastic period, c. 2600 BCE. Photo by Denis Bourez via Wikimedia Commons, used under the CC-By 2.0 license.