You can download a wide variety of custom brushes and custom fill swatches from the internet. The tricky thing is, most of these effects are copyrighted by their creators, which means you can’t resell them as stock.
Please ensure you research any custom pattern swatches, grunge brushes, stroke effects, etc you've used in your file before submission. If you’re submitting files containing effects you didn’t create you may need to obtain a signed property release from the copyright owner (for more information please read the ‘Property Release’ section in this guidebook). Images containing copyrighted fill or stroke effects will be declined as derivative artwork.
However, you’re more than welcome to create your own original effects. When submitting fill patterns and stroke effects we ask that you expand these before submission. For example, let’s say you've drawn a girl wearing a plaid skirt and have created an original plaid pattern swatch for the effect.
If you've correctly expanded the pattern fill you will see the plaid shapes clearly in outline view. An unexpanded pattern fill will only appear as an outline, not a plaid pattern. Files using unexpanded custom strokes and fills will be declined.
Examples of expanded fills in outline view:
Examples of unexpanded fills in outline view: