Great markers! Will you be offering them in different sizes? A "variety pack" perhaps? You could make each size a different color which would "help" the knitter distinguish between the sizes.
I love your color choices. The one thing I would be careful of is that there are no rough edges to catch on the yarn. I don't have my glasses on and am too lazy to go find them but it looks like you've got a small wire wrap on the bottom of some. Is that right? I would recommend either a long head pin with a very tight wrap at the top or a beading thread that you can thread through a tiny seed bead at the bottom, which will hold the rest of your beads on. You could tie a knot at the top and then use one of those handy dandy crimp covers which look like a little ball when they're attached.
Am I making sense? As a glass artist, I'm very particular about how things are finished and hope that I'm not sounding too "preachy" which isn't my intent. I just thought you might like another opinion.
You can also go to the forum www.wetcanvas.com and post your question and pictures in the glass art section. The artists there are so awesome and their critiques are always so wonderful and sensitive.