Contest sites like the one you mentioned have contributed to the degradation of the graphic design profession. Read the GDF position on crowdsourcing sites for my and many others’ views on them.
Leaving those concerns aside, what you offer is interesting and could be useful. However, repeating pattern creators aren’t something that many crowdsourcing customers would search for. They might be interested if they ran across what you’re offering serendipitously, but I doubt it would occur to many people to search for repeating patterns.
In instances like yours, you can’t assume people will find what you sell. Instead, you need to find ways to promote what you’re offering to potential customers.