Hi,
Switching isn't integrated in GNS3 because Cisco use specific ASIC for the switching (
http://www.gns3.net/documentation/gns3/switching-simulation-in-gns3/). In that way, it is difficult to emulate. Knowing that the ASIC is there for strong calculation process, and programmed specifically for switching functions, I can understand that it is very had to emulate and would need a lot of CPU/GPU power to do the same.
Therefore, only switches are implemented because they are using CPU for their operations. So, the solution to use switching commands inside GNS3 is to configure slots of Ethernet ports inside your router, and only using the switching configuration.
Frankly, it is not as powerful as a real switch (RSTP/MSTP aren't operational, some advanced VLAN options neither,...) but it is usable, and allow you to do most of the simple configurations to test the behavior of your network.
In that way, you do a sort of simple CPU emulation... I agree that it is not the proper way networks are working, but it is so nice to be able to emulate a complex network, I think this is a good "simple" solution for most cases :) At least for my "small" needs :)
For the images, I think that every ipbase have the L2 implementation, so it should be ok, no need of specific images. Not sure, but I think that most advanced switching functions not implemented in the ipbase version, are not integrated in GNS3 anyway.
They're only few differences in commands, you should have no problems. If a command doesn't exist/work, probably it is not compatible with GNS3 (look at the link above for the list of switching functions, at the
EtherSwitch Cards section)
I hope this will answer your expectations :)