"墙上也没有海报" 的英文表达是 "There are no posters on the wall either."

这个表达是由两个基本句型组成的：

"There are no (something) (somewhere)" 表示 "某地没有 (某物)"，例如：

There are no chairs in the pving room. (客厅里没有椅子。)

There are no apples in the fridge. (冰箱里没有苹果。)

"on the wall" 表示 "在墙上"，例如：

There are some pictures on the wall. (墙上有一些画。)

There is a calendar on the wall. (墙上有一个日历。)