The problem you are facing is because unlike workstations, Terminal Servers (or Citrix Servers) do NOT allow users to download printer drivers, which if you think about it makes sense.
Generally, on a workstation a user can download drivers as this will only affect just that workstation and only the users that use that workstation. On a Terminal/Citrix server you have multiple users using that same server, therefore if you do download a 'dodgy' print driver, it will affect a whole load of users - not good. There used to be a time, quite a while ago, when servers would frequently blue screen if you added the 'wrong driver'.
As mentioned previously, you could do the following:
1)... Allow users to download drivers, via a policy.
2)... Install all the necessary drivers, as an admin on that server, probably best to do this at build time.
3)... If they are Citrix servers then replicate them around using the Console, or use the Universal Print Driver.
4)... If they are simple Windows Terminal Servers, then you'll have to manually go to each and add the driver, or as an admin, simply connect to the printer, which should add the drivers. Alternatively, you could try and script it, if you have loads of printers, but this will mean copying files and exporting/importing registry keys.
You might also be able to use 'printmig' which might do the trick of getting the drivers across to all servers?
HTH