Hey.
what kind of towels are you selling? That would be the first question anyone would ask if you just put it up like how you have done here.
There are different kind of ad designs and dimensions based on where you would want to advertise.
From a marketing point of view, buyers would want to know what is different about your towels. Could be high quality egyptian or turkish cotton and you should be able to sell that through ads or banners or prints on paper, flyers, billboards or digital marketing.
I would love to work for you in creating different creatives for your towel or if you chose someone else, tell them about your USP .. most creative artist would be able to do a good job and help you. Use my above mentioned pointers as well.
Goodluck and happy towels to you.