\documentclass{article}
\usepackage{amssymb} %deck symbols
\usepackage{amsthm} %theorem environments
\usepackage{xcolor} %red color for hearts and diamonds
\usepackage{lipsum} %fill-up text
%% NOTE: I did not come up with this theorem decoration style (I've first seen it at http://denebola.if.usp.br/~jbarata/Notas_de_aula/capitulos.html) nor with the whole code (I salvaged it from TeX StackExchange and other sources over the years). This is just my current implementation of the code
\title{Poker Theorems}
\author{}
\date{}
\DeclareSymbolFont{extraup}{U}{zavm}{m}{n}
\DeclareMathSymbol{\Varheart}{\mathalpha}{extraup}{86} %add filled hearts symbol
\DeclareMathSymbol{\Vardiamond}{\mathalpha}{extraup}{87} %add filled diamonds symbol
\definecolor{deckred}{HTML}{bf0f0f} %red color
\newcommand{\vardiamond}{\mathbin{\textcolor{deckred}{\Vardiamond}}} %red diamonds
\newcommand{\varheart}{\mathbin{\textcolor{deckred}{\Varheart}}} %red hearts
\renewcommand\qedsymbol{$\blacksquare$} %change standard proof qed symbol for a filled-up square
\newtheorem{teoremax}{Theorem}
\newtheorem{spadesx}{Spades}
\newtheorem{clubsx}{Clubs}
\newtheorem{heartsx}{Hearts}
\newtheorem{diamondsx}{Diamonds}
\newenvironment{theorem}
{\pushQED{\qed}\renewcommand{\qedsymbol}{$\square$}\teoremax}
{\popQED\endteoremax}
\newenvironment{spades}
{\pushQED{\qed}\renewcommand{\qedsymbol}{$\spadesuit$}\spadesx}
{\popQED\endspadesx}
\newenvironment{clubs}
{\pushQED{\qed}\renewcommand{\qedsymbol}{$\clubsuit$}\clubsx}
{\popQED\endclubsx}
\newenvironment{hearts}
{\pushQED{\qed}\renewcommand{\qedsymbol}{$\varheart$}\heartsx}
{\popQED\endheartsx}
\newenvironment{diamonds}
{\pushQED{\qed}\renewcommand{\qedsymbol}{$\vardiamond$}\diamondsx}
{\popQED\enddiamondsx}
\begin{document}
\maketitle
\section{Introduction}
\begin{theorem}
\lipsum[1]
\end{theorem}
\begin{spades}
\lipsum[2]
\end{spades}
\begin{clubs}
\lipsum[3]
\end{clubs}
\begin{hearts}
\lipsum[4]
\end{hearts}
\begin{diamonds}
\lipsum[5]
\end{diamonds}
\begin{proof}
\lipsum[6]
\end{proof}
\end{document}
