I have a very vague idea at the moment, but maybe we can make something of it if you enjoy it. It is modern fantasy, but it is also more psychological thriller with fantasy elements:
In heaven there are a ton of people who have lived and died. They have everything they could want in heaven. They are even the chance to look down to Earth at their descendants and the way the world has progressed, but most choose not to because it takes them out of their leisure and brings back the stress of life. However, a few do chose to look (including the main character of course), and gain the desire to return to the world and help their descendants at the cost of never being allow back into heaven. If they chose to leave help they can never die in peace and become ghosts until their souls burn out. The comic is about them making the decision and then how much they should actually help. If they do decide to leave heaven, they are granted some sort of power (random) which allows them to interact with the people in the real world (think of how ghosts can transformer, lower temperature, breaking things, etc). As a twist, maybe the descendant isn't even a good person, but someone the dead person truly cares for deeply.
That's just the basic idea, if you want to change parts that will be totally fine. Tell me what you think 
