We have updated the info as indicated via the new PFD (I did however leave Bon Iver in the "acts" portion of the Eaux Claire event rather that have "(organized by Bon Iver).
Also found a more recent photo of Roger where he didn't look as young.
Tightened up illustrations all round. Added a Blood Orange to the area to the left of the Impala and Fox. Added some tentacles in some of the empty space just for fun! Was able to work in all the copy for the 6 less notable events but can make it more Hand Done/Custom once we know all that copy is correct.
Not sure how strict the color restriction is. While working on this update I was really digging this more limited color palette based on EBISU swatch, especially if we are trying to mimic an authentic psychedelic poster.
Switched gears a bit in order to allow room and better showcase the main acts. Ended up with psychedelic wave forms on the bottom to accommodate the six "less notable" events (there are currently only two to show how it could work.) I could also see some fun details added to the bottom like little boats, tentacles perhaps? We also started working in color to get a feel for the provided palette and to make sure the colors are corrct - I have added a screen shot to the colors generated by Illustrator for the provided CMYK values.
Here is a rough sketch for the illustration, just trying to convey overall layout and elements, usually I find that this style works best if you let everything build organically. Similar to the work you referenced, a lush floral psychedelic landscape with the different artists portraits layered throughout - the typography will be tucked into little breaks in the foliage or maybe inside some shapes weaving in and out.