How do I design? Firstly, there's a thought process.
For instance the final artwork of the musical Yum Sing is because of the storyline: It's about a clash of bride and groom's families with one side wanting a modern wedding whereas the other wanting to keep to the traditions.
So basically, the first step to designing is the research. After that, I comes up with the drafts of possible concepts.
The final design chosen is to show the contrast of traditional vs modern. Traditional being red and serving tea, whereas the modern is white and wine is served. (During that time, I don't think there's internet yet! So clipart availability is very limited given my resourced!)
The internal is designed like a wedding card to fit into the whole theme.
Why am I talking about this? Well, designing magic is like designing my art. I do research and I come up with many possibilities to show the effect as well as to solve the technical parts of magic. Then I experiment and finally the best concepts is used and the final show is what you get!