I am on the lookout for a database program. currently we are using access which doesn't allow a multiple user feature [I suppose it does but it is incredibly unstable] can anyone recommend a program that can allow thumbnails of image in the database?

Any real database management system (DBMS) can store binary data (known as LOB, BLOB, or CLOB fields). Binary data includes images, as well as many other types of data. The real question is not what DBMS to use, but what front-end programming environment to create the user forms, reports, etc... where you will be showing these thumbnails.

Access can actually be used fairly successfully as a front-end for other DBMSs. This works fine for smaller-simple projects, but I generally recommend steering clear of Access's front-end environment if your needs are large or complex. Web based systems are often quite successful, especially if you want to display web images such as JPG or GIFs. In that case I recommend PHP (www.php.net), but you can also use ASP, JSP, Java Servlets, Perl, or a lot of other programming environments that work with webservers.

For the actual DDBMS to use with all this:
If you want to stick with Microsoft, use SQL Server. If you don't mind an open-source (and free) solution, you can use MySQL (www.mysql.com) or (better) PostgreSQL (www.postgresql.org). If you don't mind spending a some money, there is Sybase or DB2. If you don't mind spending a lot of money, there is Oracle.