The decor of the youth room walls is always a topic of discussion among youth workers.  You want something cool and welcoming but sometimes things get dated or has been done before or whatever.  Here's an idea that should have some staying power.  Family-based youth ministry has a core belief that the youth are raised in the church family as well as the parents being involved in the spiritual training of youth.  They are all a part of the "cloud of witnesses" Hebrews refers to.  From all these "clouds of witnesses" such as all the parents, the pastoral staff, Sunday School teachers, other influential adults, collect their favorite life quote.  It could be profound or it could be silly.  All are welcomed. 

Find an artistic person or many in your church to write these on your walls.  Using actual clouds or just a graffiti-style, post each quote and who it is from. You could print them out and post them so it is temporary.  You could hang butcher block paper and write on that to make it temporary.  Or you could put them up permanently.  Craft stores have permanent markers for writing on walls so you don't necessarily have to mess with paint.