Sometimes you may need to disable the Share thumbnails generation. To do this you can set the following property in alfresco-global.properties:
system.thumbnail.generate=false
You can also turn off selected mimetype thumbnail generation using the “mimetypeMaxSourceSizeKBytes” property. If the value (KB) is less than zero, a thumbnail will be generated regardless of size. A value of 0 turns off thumbnail generation for a given mimetype.
### Thumbnail maximum size limits (KB) ### system.thumbnail.mimetype.maxSourceSizeKBytes.pdf=-1 system.thumbnail.mimetype.maxSourceSizeKBytes.txt=-1 system.thumbnail.mimetype.maxSourceSizeKBytes.docx=-1 system.thumbnail.mimetype.maxSourceSizeKBytes.xlsx=0 system.thumbnail.mimetype.maxSourceSizeKBytes.pptx=0 system.thumbnail.mimetype.maxSourceSizeKBytes.odt=0 system.thumbnail.mimetype.maxSourceSizeKBytes.ods=0 system.thumbnail.mimetype.maxSourceSizeKBytes.odp=0