TomAndJerry.html

<template>
    <template if:true={showTom}>
        <img src="https://vignette.wikia.nocookie.net/tomandjerry/images/3/33/Tom_cat.png/revision/latest?cb=20111113021359"/>
    </template>
    
    <template if:false={showTom}>
        <img src="http://pngimg.com/uploads/tom_and_jerry/tom_and_jerry_PNG56.png"/>
    </template>
</template>

TomAndJerry.js

import { LightningElement } from 'lwc';

export default class HelloConditionalRendering extends LightningElement {
    showTom = false;
}

TomAndJerry.js-meta.xml

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata" fqn="TomAndJerry">
    <apiVersion>45.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__AppPage</target>
        <target>lightning__RecordPage</target>
        <target>lightning__HomePage</target>
    </targets>
</LightningComponentBundle>