Please Remove The System Objects From My sObject List

Question is "Can I remove the system objects from list returned by describe?"

I need to identify on which all objects I can create approval process. First and only thought is to use describe and get the list of sObjects, but the problem is describe returns too many other objects on which we can not create approval process like "campaignfeed", "caseteamrole" etc.. So what is the use of showing them all. Why not we can show the list of only those object which are displayed when we create approval from native UI?

Here is the solution for this big time problem. Use this apex code to get the sObject List (use describe in a smart way)

public class ApprovalEnabledObjectsController
{
    //List displayed on UI
    public List<selectoption> supportedObject {get; set;}
    
    //Constructor
    public ApprovalEnabledObjectsController()
    {
        //Initialize
        supportedObject = new List<selectoption>() ;
        
        //Get only reference to objects
        for(Schema.SObjectType item : ProcessInstance.TargetObjectId.getDescribe().getReferenceTo())
        {
            //Excluding custom setting objects
            if(!item.getDescribe().CustomSetting)
            {
                //Adding to list
                supportedObject.add(new SelectOption(item.getDescribe().getLocalName().toLowerCase() , item.getDescribe().getLabel() ));
            }
        }
        
    }
}

Visualforce Page (Test page to show the picklsit)

Special thanks to Amit Jain who helped me with this :-)