Does is slow down page loading ? It is already at 6 seconds.
Hmm, 6 seconds isn't good nor is it bad. Where are you getting this number by the way?
So yeah, it just depends really on what you're trying to accomplish. If you optimize delivery by compressing the image and using a CDN service (optional), you should be okay. Make sure the image isn't huge or more than 2000px in size. Remember the larger the image, the longer it takes for the end user to download.