I don't know Macs but surely they have some drawing/design programs available? I've always been led to believe they were better than Windows for graphics. If you have a graphics program that you can draw or up load graph paper, you could achieve basic pattern designing.
Here are some of my tries....
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Attachment {!-- ia2 -->Star - New England 1810ish 5.JPG{!-- ia2 --> not found
Then with copy and pasting go and play with what you have got, think sideways if you cannot go straight forward
Rosemary