With the new server we now have the ability to vastly increase our ability to host images, with that in mind the new limits are:
Avatar Upload: 100kb (100px size)
Signature Upload: 200kb (200x500px size)
Profile Picture: 200kb (200px size)
Attachments: 2 MB (No px limit)
Album Upload: 2 MB (1000px size, 500 images)
If the desire is there we may increase these limits again.