Voici une solution
:
\documentclass[french]{report}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lmodern}
\usepackage[a4paper,showframe]{geometry}
\usepackage{graphicx}
\usepackage{mwe}
\usepackage{babel}
%
\begin{document}
\begin{titlepage}
\noindent
\includegraphics[width=.3\textwidth]{image-a}%
\hfill
\includegraphics[width=.3\textwidth]{image-b}%
\hfill
\includegraphics[width=.3\textwidth]{image-c}%
\vspace{2cm}
\begin{center}
\LARGE
Mon titre
\end{center}
\end{titlepage}
\end{document}
1. `\noindent` pour supprimer l'indentation
2. remplacer `\hspace{}` par `\hfill`
3. utiliser des longueurs relatives `0.3\textwidth` ou `0.25\textwidth`
