Broadly used Database Management Systems (DBMS) are not able to tackle the requirements of multimedia in querying, indexing and content modeling. Therefore, extenders for multimedia data types have been proposed. These extensions, however, offer only limited semantic modeling and rely on basic index structures which do not meet the whole nature of multimedia, for instance for a Nearest-Neighbor Search. In this context, the paper presents a methodology for enhancing extensible ORDBMS for multimedia data. In particular, we introduce an MPEG-7 Multimedia Data Cartridge which includes a semantically rich metadata model for multimedia content relying on the MPEG-7 standard. Furthermore, to fulfill the needs for efficient multimedia query processing, we created in this Cartridge a new indexing and query framework for various types of retrieval operations.