Firstly and most importantly, ensure your artwork is high resolution, that is, preferably over 300dpi! We do accept files as low as 150dpi but for best results 300dpi or higher is essential.
If you've downloaded an image or logo from google or a website it's highly likely that it's low resolution (usually around 96dpi or lower) These images will give poor quality prints and are not recommended. Our designer App will warn you if the quality of the image is below our threshold, you'll need to agree to the disclaimer shown at the time of upload in order to proceed.
For your assitance, there is a colour coded quality slider visible in the properties box when the design is highlighted or resized.
For best print results try to keep the quality slider green. See example below......

If the image is of poor or reduced quality you will be warned and would need to click the disclaimer stating you are aware and are happy in order to proceed. See example below.....
'Quality Warning'

Note: This warning only applies to image resolution and does not apply to colour matching, a more detailed explanation of this can be found below.
"Re Saving" low resolution artwork in a higher resolution copy file does not mean this will improve the quality. It simply adds the low resolution image to the new file without improvement. A good analogy is to imagine this as like taking a photograph of another "blurred" photograph. Even though the new pic is high resolution, it doesn't change the original "blurred" photograph, it simply copies it.