Your service samples are the window to your profile. You want any potential viewer to understand exactly what it is that you can provide and what is different, clever or innovative about your work, so that they'll invite you to collaborate with them.
Covering the below points will give you a higher chance of having your samples approved and being discovered by clients as fast as possible.
The goal is for your images to stand out, so consider:
If the answer is no to any of the above, then do spend time refining your samples.