Sulli,

You' ll have to go to an image editing software, Photshop, ImageSuite, Photostudio, Micro Paint may even be able to do it, and just shrink the size of the file til it' s small enough to be used.

Instead of shrinking it by pixel #, you need to use percentage.

If it' s 100%, then shrink it to 50 or so...keep doing this til you get below the 25kb limit.

The limit is set so the servers are fast and not bogged down with superly humongous signatures. Hope I helped ya.