Hi Molly,
I'm in your shoes as well. For events, we would like the invites to look like the come from someone on our sales team, so I use this -
{{lead.Lead Owner First Name:default=Ashley}} {{lead.Lead Owner Last Name:default=Smith}}
{{lead.Lead Owner Job Title:default=NetGain Technologies Events Coordinator}}
{{lead.Lead Owner Email:default=asmith@netgainit.com}}
This way, if the lead does have an account owner, that will come through. If not, everything defaults back to our events coordinator. It's important to know that I have cleanup campaigns running in a folder/program that I call database management so that if there is a first name, email, etc. for a lead owner, Marketo will automatically fill in the rest of their information.
Without that, it's possible that you could have "Bill Smith, NetGain Account Executive, asmith@netgainit.com" or some variation where certain fields were filled and other (blank) ones defaulted.
We do a similar thing for nurturing, but our emails default back to our VP of marketing.
Hope that helps!