Blurry or low quality photos will make the house look less appealing to the buyer, hence you will receive less viewings and take longer to sell.
Too much clutter and personal items do not let the buyer imagine his own things in the space and distract the attention from the actual features of the property.
Including a timestamp will reveal the exact date and in some cases also the time you took the pictures. This may not be all that bad unless your property has been on the market for months or even years which will discourage interested buyers.
Make sure the pictures reflect what the potential buyers will see if they decide to view the property. It is important also to change seasonal pictures.
If you include that the property has a garden and a pool for instance, make sure you have a picture showing that! Therefore, make sure that you include all the pictures that correspond to your description.