A covered parking space.
It is unclear to me if your question is restricted to 'What is of value to an agent from a mortgage broker"or does an agent see value in the mortgage brokers collaboratin opportunity.
Things I need to know.
1. How many buyers will you seen my way? (the 2 way street)
2. How will you insure success regarding a client I may have invested $1,500 in acquisition cost and who may represent $25,000 in future business.
3. For 35 years you were a realtor. and know what the REAL job of the realtors business is. How can you help?
Communications and process or not value items but are the product of the mortgage brokers trade.  That is why IDEAS and VALUE are the currency that elevate your offer above the cacophony of mortgage brokers.
So, what do you have?

I had a lender that would refer buyers to me, that was valuable!  I have found value from the occasional flyer or marketing piece but outside of doing a great job for my buyer clients, I haven't found a lot of value coming from my lenders.

New programs for first time buyers, statement loans for seniors with assets and limited income, construction loans, processing changes, document requirements etc.

Efficient communication and processing.  

Quick, accurate preapprovals leading to closed deals.

Communication is KEY - be responsive to my clients & me, provide great rates, have a teaching heart and get us to the Closing table ON TIME and you're golden! 

OH and my lenders pass referrals along to me too!

Exceptional service: getting the job done, going the distance, responsive - answer phone, emails, text messages. I have all that with my preferred lender.

I do not expect referral business from my lender any more than I would expect referral business from my escrow officer. 

Clear communication, available on weekends, responsive.

I would love to have a lender who can send me buyers, so far it's been a one way street. Also a lender who can take care of buyers who needs a little work.  I notice some lenders don't want to bother assisting someone who needs a little help or at least, refer that buyer to someone else who can assist.  I want my buyers to be taken care of by my business parters just as good as I take care of them. 

Constant follow up with prospective home buyers.

new programs that could help buyers is my interest.

This is too broad a question.

As a seasoned operator...I value my like kind

Welcome Natalie

Besides exceptional customer service and responsiveness, doing what you promised to do and keeping me in the loop. I love receiving updates before I had the chance to request them! 

Yes, an occasional referral would be greatly appreciated but so is sharing listings or blog posts on your social media.