This might sound lame,

but you could always do the theme "We are Family" and put lyrics from the song up there.
Here are the lyrics:
We Are Family
Sister Sledge
(CHORUS

We are family
I got all my sisters with me
We are family
Get up ev'rybody and sing
Ev'ryone can see we're together
As we walk on by
(FLY!) and we fly just like birds of a feather
I won't tell no lie
(ALL!) all of the people around us they say
Can they be that close
Just let me state for the record
We're giving love in a family dose
(CHORUS x2)
Living life is fun and we've just begun
To get our share of the world's delights
(HIGH!) high hopes we have for the future
And our goal's in sight
(WE!) no we don't get depressed
Here's what we call our golden rule
Have faith in you and the things you do
You won't go wrong
This is our family Jewel
(REPEAT CHORUS TO FADE)
Like I said, you could pick and chose some lyrics, type them up and put them around, like a collage. Then put tons of pictures from the chapter. Pictures from Bid day(s), date parties, Diamond ball(s), Initiation (afterwords obviously), philanthropy's, and just lounging around.
You could also put things from our creed (ex. I believe in Alpha Delta Pi, I believe that my sorority is more than a ritual or a symbol, that it is a way of life).
You could also put up a picture of Alphie, what would be perfect is if you have a picture of sisters with an Alphie, then you could "say", "so and so with Alphie, our mascot".
You could also put violets up, say these are the official flower.
I'm starting to ramble, so I'm going to shut up now. I'm sure I could think of more though