I think the best way to make your mark is by doing research, find out which cookies sell in your area. This will give you an idea of where to begin.
Look at seasonal trends which can involve different spices and blends and also look at them visually by trying to make them as inviting as possible. Adding colour, icing, coloured sugars, glitters and textures, adding crunch etc. Making them themed, or brightly coloured add swirls and patterns to them. Possibly look at how you can infuse flavours into them.
Pinwheel cookies are easy to make and draw attention to themselves, tea-infused cookies are for the more sophisticated palette, and then you have the oreo flavoured and decorated shortbread cookies that will also make an impact.
Also look at old-school recipes, like things your Grandma used to make, cookies that take you back to childhood days.
Work out your market, and who you are looking at selling them too, children love colour and soft cookies whereas adults will want something a little more sophisticated.
Making the cookie visibly exciting is a key to a sale or make it with a mouthwatering ingredient, and they’ll fly off the shelves.
The best way to get a read on your cookies is to make them for family and friends and gauge their feedback on them. Then look at making them for other people that don’t know you, ask fb friends what they’d like to see in a cookie and it may inspire your recipes. Experiment have fun and see what you create.
For summer cookies you could look at citrus fruit flavours by adding zest etc whereas in winter you could look at mixed spices, cinnamon etc.