I used only Million Bells in my hanging baskets this year. I tried two ways to get the side plantings in: from the outside and pushing in--which was messy and from the inside to the outside, much less messy, but you have to be very careful not to break off the plant, was much less messy and made the basket look much nicer. I'm sure it won't matter in a couple weeks, but here we are today.
I'm doing a bright pink, deep purple, and bright yellow theme this year. When I side planted, I took a box cutter and slit a small "X" in the liner and then put the plant in the basket. I varied the level in the side that I put the planter where I put the side planting. You can see the yellow in the far bottom, the pink in the middle and it's kinda difficult to see the purple on the far left ins on the top level of the basket. Not sure if this will effect the side planter look, but I thought I'd try it out.
Here is my matching window boxes. I added a spike in the middle and a bright green potato vine in the corner. Again, bright pink, purple, and yellow.