Raw Source
Ahab / your helmet/mask of choice replace 

// ==UserScript==
// @name your helmet/mask of choice replace
// @namespace torn.com
// @include *www.torn.com/loader.php?sid=attack&user2ID*
// @author Ahab [1735214]
// @version 1.0
// @license MIT
// @require https://greasyfork.org/scripts/5392-waitforkeyelements/code/WaitForKeyElements.js?version=115012
// ==/UserScript==

/*
278 - Kabuki Mask
412 - Sports Shades
413 - Mountie Hat
414 - Proda Sunglasses
538 - Medieval Helmet
598 - Witch's Hat
608 - Santa Hat
621 - Snorkel
641 - WWII Helmet
642 - Motorcycle Helmet
643 - Construction Helmet
644 - Welding Helmet
647 - Leather Helmet
651 - Combat Helmet
726 - Scrooge's Top Hat
806 - Old Lady Mask
807 - Exotic Gentleman Mask
808 - Ginger Kid Mask
809 - Young Lady Mask
810 - Moustache Man Mask
811 - Scarred Man Mask
812 - Psycho Clown Mask
813 - Nun Mask
828 - Donald Trump Mask '16
841 - Classic Fedora
869 - Elon Musk Mask '17
921 - Michael Myers Mask '18
926 - Gronch Mask '18
927 - Baseball Cap
931 - Bush Hat
935 - Cork Hat
937 - Fisherman Hat
1013 - Jigsaw Mask '19
1026 - Party Hat '19
1036 - Greta Mask '19
1037 - Anatoly Mask '19
1038 - Santa Beard
1043 - Paper Crown : Green
1044 - Paper Crown : Yellow
1045 - Paper Crown : Red
1046 - Paper Crown : Blue
*/

var t = ['278','412','413','414','538','598','608','621','641','642','643','644','647','651','726','806','807','808','809','810','811','812','813','828','841','869','921','926','927','931','935','937','1013','1026','1036','1037','1038','1043','1044','1045','1046']

function mask(){
    $.each($("div[id^='attacker'] img[src^='/getImage.php?ID=']"), function(){
        if(t.includes(this.src.split('=')[1].split('&')[0])){
            $("div[id^='attacker'] img[src^='/getImage.php?ID="+this.src.split('=')[1].split('&')[0]+"']").attr('src', "https://i.imgur.com/ycGLFN2.png")
        }
    })
}

waitForKeyElements("#attacker", mask);