You can add new patterns via the pattern docker, or the pattern-quick-access menu in the toolbar.At the bottom of the docker, beneath the resource-filter input field, there are the Import resource and Delete resource buttons. Select the former to add png or JPG files to the pattern list.
Krita also allows you to make custom gradients and custom patterns. Since the location of my last explanation of custom gradients isn't obvious (it's in the layers management tutorial), I'm repeating it here:
As for the patterns, they are image files inside a folder, to install them, click on the pattern button in the main toolbar, then click on the left button in the bottom of the popup, then just select all the patterns you want to install.
KXStitch is a program that lets you create cross stitch patterns and charts. Patterns can be created from scratch on a user defined size of grid, which can be enlarged or reduced in size as your pattern progresses. Alternatively you can import images from many graphics file formats which will allow you to reduce the number of colors and to restrict the conversion to full stitches or optionally use fractional stitches. You may also use images as backgrounds allowing you to trace over them. These imported images can then be modified using the supplied tools to produce your final design.