Your not the only having problems, with uploading pictures.
I also tried to upload my pictures and been denied several times, but after several trials and error I have uploaded 2 pictures.
Just keep on trying
A tag is a word that if someone searchs that word it will bring them to your item. so like the tag for this could be "tag help" "tag info" so on and the more you have the more likly people are to see it.