WOW! I'm impressed that you would ask this question. I work for a (high end) photography studio and am amazed at what people wear to have their portrait done. Something they are paying hundreds to thousands of $'s to buy, something they are planning on displaying in their home for the next 50 years... well, let me just say it makes me cringe.
I can't tell you the background for the Roundtable, but last years
MVMCP was blue with snowflakes and characters added (smowman, Mickey).
Here is what I tell my customers:
Stay away from bright and bold colors and busy patterns, it will bring attention to your clothes instead of your faces. Everyone in the picture does not need to match in color, but stay in the same hues. Although we all love Winnie the Pooh, when Winnie the Pooh is on the shirt that is all people will see. Sleeves or at least partial sleeves are best. Females in general do not like how our upper arms photograph.
In general, solids work best. Then go with colors that work best for your family skin tones.
Have a wonderful visit! I'm sure your pictures will turn out great!
