I think it's sad that it's more socially acceptable for girls to like 'boy-ish' things, than it is for boys to like 'girl-ish' things.
I've taught many girls who loved Star Wars, superheroes, Dr Who etc. - they were all either a)regarded as having cool bags/jackets/clothes on non-uniform etc.; or b)it didn't register at all and nobody made a comment. These were all 6 and under.
I had one 3 year old boy who would come straight into nursery and put on a princess dress from the dressing up and wear for the rest of the session. The other children were absolutely fine with it - a couple commented initially that "he's got a dress on", but it was otherwise fine. His mum knew, but other parents would've commented, so he had an extremely boy-ish coat that he wore to come and go.
I took my 3 year old nephew to buy some pumps/plimsoles recently - he picked up the spakly ones (that were more like ballet shoes) and asked for his size. He tried them on, commented on how sparkly and pretty they were, but said, "I can't wear them at nursery, they're too sparkly". He chose red Velcro pumps instead. It seemed to be a practical choice rather than gender bias!
If my son wanted a pink bag, I'd let him have it as long as they understood some silly people might think it was silly for him to have it and he just had to say he liked it anyway.