Not sure why I felt the need to share this, but here goes:
My younger brother passed away about 15 yrs ago in a drowning accident. At the time of his death, in his early 20's, he was an aspiring artist. Needless to say, my mother chose to hang some of his paintings in the house.
Two years ago at Christmas, there was a larger than usual gathering of family for Christmas dinner at her house, I was there also.
I remember having a great time visiting with all those I had not seen in years. At some point, I left the living room to go into the kitchen to get something from the table(probably a cookie...urp) I was the only one in the kitchen and as I turned to leave I noticed some movement from the corner of my eye. A painting which my brother had done, was swinging wildly from side to side from the nail which it hung on the wall. Always the realist, I walked over to investigate. The picture was still swinging, when I approached. There was no wind, no breeze anywhere and being winter, all doors and windows were sealed. As I stared the painting slowly stopped swinging on its own. Again I checked for air current all around the painting and could find none. Wierder yet, as I watched it swing, it made no noise whatsoever. When I tried to recreate the swinging motion by pushing the painting with my hand, it scraped loudly on the wall behind. OK, so with the hair on the back of my neck prickling, I went back into talk to mom. I told her what happened to see her reaction. To my unnerving, she never batted an eye, just smiled and said something like, "I'm so happy your brother could join us."

i think if i were you and my mom said that i would throw up!

I wouldn't define what happened as "poltergeist" but more so as an active spirit visiting. Poltergeists generally are destructive in nature and come more so from a "host". Ususally this host is a young person, around puberty with issues and things like that to deal with. The notorious "they" say that poltergeist activity is actually a physical manifestation of psychologial issues.

It is possible that your brother was visiting for the holiday. Was that a special time of year for him? Was that particular picture of special significance to him?

Your mom probably reacted the way I would have - she probably felt genuinely touched by divinity knowing that her son was able to communicate a little "hi-I'm here". As long as the activity is not negative or hurtful in nature, just smile and tell him hello and that you love him. That's probably what he wanted to tell you.

God bless.