When uploading images into posts, post attachments or to the Gallery, file sizes are very important. Image files taken from digital cameras etc. can be very large and will take a long time for you to upload and consequently a long time to dowload so that they can be viewed in the post etc. Best practice is to downsize your images to something like 800 x 600 (they will be plenty big enough at this size) before uploading them. You will find a big improvement in upload speeds and also the time it then takes for your images to be veiwed in your posts etc.