If you received a 'Maximum Request Length Exceeded' error when uploading an image to Core iQ, that is typically tied to a file size limit being exceeded. JPG images must be below 1.5-2Mb in size. Anything above that size range will create an error in Core iQ when you attempt to upload the file. Lower the size of your image file and then attempt to upload the item again into the Image Library.
Errors can also occur if you upload an image with an invalid file name. This is typically due to some sort of special character like an apostrophe or another character (i.e. #@$%&). Simply remove the invalid file and upload it again without the special character in the name.