See this page for a description of how documents are defined using schemas. The schemas contain the fields that are available for a given Document type. So if you want all the properties of a specific asset (e.g. a picture) then have a look at the picture document definition (to find all included schemas) and then you can look at the schemas (and all the facets) to find all the fields. You have to check facets because they can also have schemas defined.

For example, a DAM Picture asset… – document definition –

<doctype name="Picture" extends="Document">
  <schema name="common"/>
  <schema name="uid"/>
  <schema name="dublincore"/>
  <facet name="MultiviewPicture"/>
  <facet name="Picture"/>
  <facet name="Versionable"/>
  <facet name="Publishable"/>
  <facet name="Commentable"/>
  <facet name="HasRelatedText"/>
  <facet name="Asset"/>
</doctype>

And the Asset facet has

<facet name="Asset">
  <schema name="dam_common"/>
  <schema name="ip_rights"/>
</facet>

Match schema names to the underlying XSD files and you have a list of fields for a Picture asset. Repeat for other document types.