\documentclass{scrartcl}
\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{blindtext}
\newenvironment{Klein}{\tiny}{\normalsize} %Ohne Argument
\newenvironment{Neu}[1]{\vspace{#1}\tiny}{\normalsize} %Mit Argument
\begin{document}
\blindtext
\begin{Klein}
\blindtext
\end{Klein}
\blindtext
\begin{Neu}{2cm}
\blindtext
\end{Neu}
\end{document}