The style guru - who has dressed figures such as Beyonce, Kylie Minogue, Gwyneth Paltrow and Cheryl Cole - said the fancy costumes helped draw him to be a contestant on this year's series, as well as the chance to learn something new.
Macdonald, 42, said he will not hold back if the judges lay into his abilities.
"Whatever they give me I'm going to give them back. If there's one thing I never understand when I watch the show is when the dancers and celebrities take beatings from the judges and don't say anything.
"If it's constructive feedback then fair enough. I'm going to give it my best shot and work hard, but I'm definitely not going to stand there and let Craig lay into me. I'm not afraid of the Revel Horwood."
Macdonald - who was named British fashion designer of the year in 2001 - has already appeared on Strictly spin-off show It Takes Two as the resident style expert.
He said: "It's an amazing opportunity - the journey, the people you will meet, the fact viewers will get to see my personality and the funny side of me. I will be able to dance, hopefully, by the end of it - and that's why I've ended up doing Strictly."
Macdonald went on: "I've spent my entire life dressing a variety of different people from all different backgrounds, shapes, sizes and ages. For once in my life, somebody gets to dress me. For me, I like the fact I can have the sparkles and the crystals and the glamour that I've spent my life putting on other people.
"I'm loving the rhinestones and lace and the crystals. I just want more and more. I'll probably look like a Christmas tree by the end of it."