The writer only gave a thumbnail sketch of his characters.

这位作家对他作品中的人物只作简略的勾画.

The novelist only gave a thumbnail sketch of his characters.

这位小说家对他作品中的人物只作简略的勾画.

It's a thumbnail sketch of how the justices weighed the case.

这是一次法官们权衡案例的简单概况。