For me I like a "big" mare, lots of hip, bigger bodied and substance.. I am not a fan of the overly extreme/refined horses out there, I like mine to look like big stock horses shrunk down.. Here's a few of our gals:
I think you said you were planning to breed for the all around mini that can do well in halter and performance, including driving? That was exactly our plan although we have now stopped breeding and use our minis in 4-H, therapy and showing. I do like the mare to be bigger than the stallion and a good hip is important, but then so is conformation in general. I like the conformation to be balanced and the legs to be straight, with correct angles. Here are recent pics of two of our broodmares: the bay and white has had at least 6 foals and the black and white has had 9 pregnancies and came in second (to our two year old) in a huge mini halter class the day the pic was taken.
Someone mentioned dwarfism, and the bay has been tested N/N (negative) for the 4 ACAN dwarf mutations. I highly recommend you consider only buying tested minis to avoid frustration and heartache. Frustration because one of the mutations (D1) combined with any of the 4 mutations produces early fetal death which may manifest itself as a mare that you thought was bred but comes back into heat.
MiniAmateur, Nutmeg is my favorite (just don't tell the others or their feelings will be hurt) The very moment she was born I was in love. She is a big bodied strong mare but gives me goosebumps when she moves. She has that 'hang in the air' big hesitating trot, and when she flags her tail and snorts... she just amazes me. She will be 15 this spring! I don't know where the time has gone.
My friend has my ideal brood mare, i've seen her foal and he is to die for. I think she bred her this year and if so i'm first in line for the foal lol
My classic mare , Kahle's Sparkle.....will post her two colts she has produced for me as well ... no new pictures of Sparkle but this is a couple years old.