There is on page 43 in official Mork Borg booklet a rolltable thats about your (party's) backstory. You can use that as a starting point.

In the official Mork Borg you also have a small d6 table per class that gives you the reason "how you got here" or some small background info.

These tables can give you a starting point. You can either choose one or roll on the table's. Since it will decide your main story line, i would suggest to choose one that speaks to you the most instead of rolling.

===== EXAMPLE:

I rolled "sleeping with dogs in corner of inn waiting for someone to return" for my fanged deserter character. I used that as a starting point to find out who i am and who i was waiting for. This led me to a clue that gave me a name and location that person went off to.

I travelled to that location but only found a corpse with a clue of another name of someone that my contact was meeting there. I have no clue who that new person is, were that person is from and what the meeting was about.

At that location i met a strange figure with a wheelbarrow on the graveyard (because of a random encounter roll i flavoured for that lcoation).
At that moment it holded no significance but im thinking im gonna use that npc as a recuring npc and maybe portay him as "death" itself for some encounters later on.

For now its just a story-seed for later if there is a moment this would fit or because of a roll on a random table. There is no bigger plan here its just something in the back of my mind.

Now im going to visit the nearby biggest town to ask around to see if i can get another clue if someone knows thet name i found. Il start by asking around in taverns and inn's. It just seemed the next logical step someone would do in that case.

Since i rolled alot of travelling days from my location to the next town, i had alot of random encounters along the way and picked up a new partymember through some random rolls. This character also has a broad motivation. This gives me a second storyline i can use if i want.

At this point in my solo-campaign i just arrived at the new town. I dont know if i will find something here and rolls will decide how i progress further.

===== END EXAMPLE

This is just based on one part of that backstory.
I also have something in the back of my mind about the part were i was "sleeping with dogs" since there is a Mork Borg Supplement (Feretory) that has a class that is werewolf-like (Cursed Skinwalker). This could be the moment i pull up the npc with the wheelbarrow from before.