As Lemon stated previously, this is most likely a missing or corrupt file error with your PBE/Live Client, repairing it should fix any and/or all missing texture files. It happens occasionally and is easily fixed, although somewhat time consuming. If repairing your client does not fix the issue, file a support ticket through support tab in the upper-right next to the account button. After getting onto the support page, click on the 3rd tab to the right, where it says "Submit a request." If nothing else helps, Sit on your hands and swing your legs wildly while pouting, this should make you laugh.
~Summoner namora, of the lower case.