Users of PicToWeave are restricted by copyright laws.
You cannot use the work of another person or create a derivative work without their permission.

Therefore you are in breach of copyright if you take a copyright photo or other image and create a weave pattern from it without the permission of the copyright holder.
Likewise, unauthorized conversion of commercially available weave patterns in other formats, either electronic or hard copy, for use in PicToWeave is a breach of copyright.

Just because you see something on the internet does not make it public domain.
Nor is it a legal requirement to display a copyright symbol in order to claim copyright.

EDIT:

Suggested reading:

Australia
Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to or

United States
Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to or