Well, clearly Beth and Carl are the main characters. Beth was known for her kindness and musical talent in the original show. Carl was Rick's son, a young boy growing up in the apocalypse, learning how to survive and protect his family.
One interesting storyline could be Beth and Carl going on a secret mission to find a rumored safe haven. They might face many challenges along the way, like avoiding herds of walkers and dealing with other survivors who have less than noble intentions.
Maybe Carl and Beth get separated from the group and have to rely on each other completely. They encounter a strange group of survivors who seem friendly at first but have a dark secret. Carl's skills with a gun and Beth's medical knowledge help them outwit this group and find their way back to their own group. Along the way, they grow closer as friends and develop a deeper understanding of each other.
Unfortunately, Carl did die in The Walking Dead comics. It was a sad moment for fans. His death had a big impact on the storyline and the other characters.