[Leonyipa]

How to set a maximum size(width and height) for signatures,
so user will not put oversized and very long images into their signature?

[Stephen Edgar]

That is an issue you should raise with the plugin author on their support forum if you want a feature implemented.

[Leonyipa]

ok, I now switched the post in:
https://wordpress.org/support/topic/gd-bbpress-tools-signature-set-maximum-size?replies=1