trigger attachmentTrigger on Attachment (after update, after insert) {
string placeholder = '<img alt="{0}" src="/servlet/servlet.FileDownload?file={1}"></img>';
list<contact> contactToUpdate = new list<Contact>();

for (Attachment att :trigger.new) {
    if (att.ParentId.getSobjectType() == Schema.Contact.SObjectType){

        List<String> fillers = new String[]{att.name,string.valueOf(att.id)};
        contactToUpdate.add(new Contact(id = att.ParentId,
                                        pname__c = att.name,
                                        picture__c = String.format(placeholder, fillers)));
    }
}
update contactToUpdate;
}