I started drawing this as an exercise to explore when better to use the Pen tool, the Brush tool and the Pencil tool to make your desired lines in Adobe Illustrator. There was no notion of a fairly completed work emerging. Since I enjoyed the challenge, learn from it and in fact am pleased with the final outcome, I decided to post it on here for record.

Of course it has nothing really to do with that great giant of art & taste Alphonse Mucha, but I felt it gave a nod to him with in having a female character to the fore, with circular repeated patterns and floral motifs. 

Clipping masks were used to house the patches of shading of the main figure within her body (the clipping mask). Ah I'm going to correct myself - I could have done that, but I actually changed the drawing mode after creating the body outline to the Draw Inside mode. I created the flowers very quickly with the standard Brush tool. Below that I created a layer for blocking in the flower colour, which I did using the Blob Brush tool.

Radial elements were created in one of two different ways. If the decoration was to appear at certain spaced points, I grouped the ornament's contents and used the Rotate tool to move them radially from the centre. The way you ensure that is to have the group selected, choose the Rotate tool, then with mouse left click on the centre whilst holding down the Alt Key - this defines the central point around which the Rotate tool will calculate from. Up pops the Rotate tool dialogue box, asking how many degrees do you which to rotate from the current position. If you want 20 iterations, you can type in 360/20 and let Illustrator calculate what degrees that is. 

Once you've set the degrees, the important bit is to click the Copy button. This will create a Rotate transformation as a copy, leaving the original where it is. 
Now for the fun bit - you repeat that copy sweeping round your point by repeatedly pressing Cntrl D to duplicate that transform until you go full circle or as far as you like!

The second method I used when the copies have no spacing around them, was to create a Pattern brush and apply that to the path of a circle. For elements which did require some spacing, I created a straight horizontal path with the Pen tool, and spaced out my elements on this path, then made the path have no stroke but keeping it in the definition of the Pattern brush.

 

woman modern mucha8