There are different types of modules that can be specified in HG. For a standard X10 module, the primary ones are light, dimmer, switch. If you pick light, then it's an on/off type module and will only have those controls in the interface. If you pick dimmer, then you will also get a slider bar to pick the dim state. If you choose switch, the icon is different but I'm not really sure it operates much different. The 3 types send the same command when turning on/off a module but they are treated slightly differently in code so the difference does matter if you get into scripting. X10 doesn't really have switches that you would need to control, so I would suspect your entire setup could be defined with lights and dimmers.
Now, that may cause issues when it comes to using HG as far as appearance but not functionality. If you had an attic fan in your setup and it looked like a light, that might be confusing. You can change the icon to something different as well, but I have not played with what's available, so I don't know how extensive the options are. Again, functionally it will work fine with any icon.