I've been visualizing a globe then slowly expanding the space to include stars, then galaxies.

The issue is I feel this visualization of inanimate stuff may not elicit the feeling of good-will as strongly as visualizing an actual sentient being.

What do you visualize when wishing well for all beings?

Hmm, by the time I wish for anything that abstract, I'm just tuning in to the feeling and relaxing, smiling, letting it pervade. I feel like a hot stove.

Are you a very visual person for whom visualization is important? I'm a poor visualizer, so mental images are not the main thing for me, but maybe you can translate what I describe to images that would work for you?

I tend to think of how it feels to be left out and hurt and without food and shelter and belonging and how every sentient being shares those basic needs and how not having one's needs met makes it so much harder to do good. Then I think "Would I want that for the world?", to which the answer is no, and then I can more easily imagine wishing well to a number of different cases - real ones and fictional ones - that I would otherwise have difficulty in wishing well. And so I think of a number of individual cases until it feels like a general principle, because if I can wish those extreme cases well, then it has to be general. Something like that. 

The people who I have an aversion to.

May I be Well, May I be Happy, May I find True Peace.

May (Individual Loved One) be Well, May she be Happy, May she find True Peace. (Take the time to focus on each close Loved One individually) 

May [Individual Friends] be Well, May they be Happy, May they find True Peace.(Take the time to focus on each friend individually) 

May all Living creatures (name some, ie. animals, plants) be Well, May they be Happy, May they find True Peace. 

May all Things be Well, May all Things be Happy, May all Things find True Peace. 

May all things Outward AND Inward be Well, May all things Outward AND Inward be Happy, May all things Outward AND Inward find True Peace. 

May I be Well, May I be Happy, May I find True Peace. 

In each instance hold the object/person in your mind for inspection, will Good toward them, and reflect on their challenges to achieving that Good. Reflect on what and how they would experience life differently with more Wellness, Happiness, and True Peace. Honor the experience, and grow in gratefulness that you have the opportunity to have it.

Ha! I'm getting recently images of some people in meditation that I was either hurt by in the past or my actual neighbors with whom we have issues (too much noise after midnight). 

Thier image pops up in the image (Mind) space and I note that unpleasant feeling, body sensation associated with it, note ill will, and finish it up with wishing well for that person. 

I don't do Metta practice as such. But I do wish well to all and any image that resembles a sentient being, insect, rat, tiger, fish or human and move on noticing whatever else pops out in awareness. 
I do say the wishes both before my practice and after, that my practice be of benefit to all beings. 

I feel like various people and interactions will pop into my head and I'll just kind of go with it. It can be family members, or friends, sometimes enemies. If it's an enemy I'll try to imagine what it would feel like to make amends with that person (to varying degress of success).  Or if it's a friend or family member, what would it feel like to share a moment of love with that person?  Or, if it's Sangha, or someone spiritually inclined, what would it feel like to share Dharma with that person?