As Mark stated, there currently is no option for Pattern Fill colors. But I believe this was done intentionally, as Pattern Filled colors are not great for Data Visualization.
I couldn't find this in the Idea Section (Truth be told I didn't look exceptionally deep), so you could add it there. This will get it on the Devs radar.
I suppose that works. I usually associate differences in gradient (i.e. shade) with a difference within a measure, but in this case you used it to show the different segments (i.e. a dimension). It's not exactly what I was hoping for, but I might be able to make it work. Another opinion, I suppose, would be to import my own color palate that contains pattern alternates for each of the colors I need and manually assign them. That seems extra tedious though. Thoughts?
Custom palets only support Hex Code colors...
unrelated, but @MarkBradbourne I noticed that you tweeted on @data15. Which sessions are you most looking forward to?
50 Shades of Data, Advanced LOD Calcs, Jedi Calcs, and Getting Your Performance Up come straight to mind... I'm also pre-registered for Everyone Loves Sets