From Wiki of the E-Business and Web Science Research Group

GoodRelations is a standardized vocabulary for product, price, and company data that can be embedded into existing static and dynamic Web pages.
Project Main Page Vocabulary Documentation Developer's Wiki GoodRelations Cookbook

Adding Images to Offers and Products

Very often, we want to attach images to offers (instances of gr:Offering) or products or services, which can be instances of

• gr:ProductOrServiceModel,
• gr:ProductOrServiceSomeInstancesPlaceholder, or
• gr:ActualProductOrServiceInstance.

The standard way of doing so is using the foaf:depiction and foaf:thumbnail properties. The advantage is that many Semantic Web and LOD tools can automatically display such images.

Note that Yahoo SearchMonkey recommends the media:image property for attaching images, which is a proprietary Yahoo element.
(Definition from 1: An image of something. Use this property to relate a document to an Image object embedded in it or in general to relate an object to an image representation of that object.). Also, rdfs:seeAlso can be used.

If you want to be on the safe side, use all three.

Example in RDFa:

 
<div typeof="gr:Offering"
  xmlns:gr="http://purl.org/goodrelations/v1#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:media="http://search.yahoo.com/searchmonkey/media/" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
  xmlns:foaf="http://xmlns.com/foaf/0.1/"
  xmlns:use="http://search.yahoo.com/searchmonkey-datatype/use/">
 
  <div rel="gr:hasPriceSpecification">
      <span property="gr:hasCurrencyValue">99.99</span>
      <span property="gr:hasCurrency">USD</span>
  </div>
  <div rel="gr:includesObject">
      <span property="gr:amountOfThisGood" datatype="xsd:float">1.0</span>
      <div rel="gr:typeOfGood">
          <div typeof="product:Product gr:ProductOrServicesSomeInstancesPlaceholder">
              <span property="rdfs:label">Hepp Computertechnik Personal SCSI Controller</span>
              <span property="rdfs:comment">Fast 16-Bit SCSI Controller for PCs</span>
              <span rel="rdfs:seeAlso media:image foaf:depiction">
                  <img src="http://example.com/product.jpg"/>
              </span>
          </div>
      </div>
  </div>
</div>
 

Note 1:

• The namespace prefix foaf: stands for http://xmlns.com/foaf/0.1/.
• The namespace prefix media: stands for http://search.yahoo.com/searchmonkey/media/

Note 2:

• If it is important for your data to remain within OWL DL, you must either import OWL DL ontologies that define those properties or define them as owl:AnnotationProperty or owl:DatatypeProperty.

Example 1 in RDF/XML (just foaf:depiction and foaf:thumbnail):

 
<gr:ProductOrServicesSomeInstancesPlaceholder rdf:about="http://www.stalsoft.com/dip/bookmashup/books/0387485309">
   <rdfs:seeAlso rdf:resource="http://www.amazon.com/Semantic-Web-Real-World-Applications-Industry/dp/0387485309"/>
   <rdfs:label>The Semantic Web: Real-World Applications from Industry (Semantic Web and Beyond)</rdfs:label>
   <rdfs:comment>The Semantic Web: Real-World Applications from Industry (Semantic Web and Beyond)</rdfs:comment>
<!-- Add this -->
   <foaf:depiction rdf:resource="http://ecx.images-amazon.com/images/I/51EOLmd5yQL.jpg"/>
   <foaf:thumbnail rdf:resource="http://ecx.images-amazon.com/images/I/51EOLmd5yQL._SL75_.jpg"/>
<!-- Add this -->
</gr:ProductOrServicesSomeInstancesPlaceholder>
 

Example 2 in RDF/XML (including media:image):

 
<gr:ProductOrServicesSomeInstancesPlaceholder rdf:about="http://www.stalsoft.com/dip/bookmashup/books/0387485309">
   <rdfs:seeAlso rdf:resource="http://www.amazon.com/Semantic-Web-Real-World-Applications-Industry/dp/0387485309"/>
   <rdfs:label>The Semantic Web: Real-World Applications from Industry (Semantic Web and Beyond)</rdfs:label>
   <rdfs:comment>The Semantic Web: Real-World Applications from Industry (Semantic Web and Beyond)</rdfs:comment>
<!-- Add this -->
   <foaf:depiction rdf:resource="http://ecx.images-amazon.com/images/I/51EOLmd5yQL.jpg"/>
   <media:image rdf:resource="http://ecx.images-amazon.com/images/I/51EOLmd5yQL.jpg"/>
   <foaf:thumbnail rdf:resource="http://ecx.images-amazon.com/images/I/51EOLmd5yQL._SL75_.jpg"/>
   <rdfs:seeAlso rdf:resource="http://ecx.images-amazon.com/images/I/51EOLmd5yQL._SL75_.jpg"/>
<!-- Add this -->
</gr:ProductOrServicesSomeInstancesPlaceholder>