The only sizing available is by changing the gauge; a worsted weight will make a fairly large sweater, and a sport weight will make something quite a bit smaller. The body is 180 stitches around, so for a smallish sweater (34" around), you'd want a yarn and needle size to give you about 5.25 stitches per inch, maybe sport weight. For a larger sweater (45"), use something at 4 stitches per inch, like a heavy worsted. SWATCH SWATCH SWATCH because the only control you have over the size is the gauge. Even I didn't learn this very well, because the large sweater was extra large until the recipient accidentally felted it, and the small one was a little tight (the chain stitch outline makes the knitting less stretchy than it would otherwise be). Note that length is currently proportional to width, but you can add and decrease that by pasting in more pattern on the body. The sleeves are probably too much work to adjust the length of, sorry.
Pick three colors for the lizards, and a fourth contrast color for the cuffs and ribbing and outlines. Knit the ribbing in the contrast yarn in the ribbing of your choice for as long as you want, and then knit the main pattern in stockinette. I did mine with bobbins, intarsia-style; you could probably try to carry the colors, but three strands will make it pretty toasty.
Knit all the pieces. Note that the colorwork pattern for the front doesn't have the neck hole marked; steal the collar bind off / decreases from a sweater pattern in a similar gauge that you like the collar of. Sew the pieces, pick up stitches for the collar, and knit that in the contrast yarn. Outline all the lizards in chain stitch with the contrast yarn, with a crochet hook or a needle.
