This is the fanart by Earthrock, a Slayers doujin artist.
I love his doujinshi very much, because his Zel is always serious, and Lina and Ameria are always cute.
The kana in the image is for Slayers, and kanji are the name of his doujin circle, "Tennen Chikyuu-do" (Natural Earth).
This isn't a CG, but a scanned image of B4 size of drawing, that was used as
an advertizing at the Comiket 58 and 59 in 2000.