As a recent alum I understand where you are right now.
My best advice is that you should lead by example. If you set the precedent for others to follow, then they will follow your lead. If you tell obstinate college kids what to do, forget it
Your role now is to step back and let the organization continue, contribute if they ask or if they need it. Don't offer unwanted advice.
Try to show people how the organization can be better, don't tell them.
I'm kind of in a similar situation. I'm hanging around waiting to hear back about jobs. In the mean time, I'm helping out with the chapter. Recently, I led the first two candidate class meetings (taught them how to run meetings, helped them elect officers, then turned it over to 'em). This was helpful because it let the active brothers attend their chapter meeting.
I used to always notice we never had pictures of anything. So I bought a digital camera and have been taking LOTS of pictures. Found a great website where I can get 'em developed cheap.
If you have an alumnae chapter/organization you do have the opportunity to hold a special place there. Often, alum organizations help mentor officers in the active chapter. There are really many roles that you can fill.
The key to being a contribuiting alum is having the patience, the tact and the discretion to know what to say and when to say it.