Here's my attempt...
I changed the middle column of the table from an l column to a p{5.2cm} column. That puts the cells in that column in a paragraph of width 5.2cm (change that according to your image size).
I put \vspace{0cm} before the image. Don't ask me why, but it seems to work ok!
Result:

Code (the demo option makes the black image placeholder):
\documentclass[demo]{article}[12pt]
\usepackage{graphicx} % This is already loaded by the atlasnote class
% Just use it to include your plots!
\begin{document}
abc
\begin{table}[h!]
\begin{center}
\begin{tabular}{|c|p{5.2cm}|c|}
\hline
ABCD, put me at the top &\vspace{0cm}\includegraphics[height=2.5cm]{invariant_mass_eX_Asymmetric} &line1, i wish to be much more at the top\\
& &line2, idem\\
& &line3, idem\\
& &line4, idem\\
\hline
\end{tabular}
\end{center}
\end{table}
def
\end{document}
Update
In response to the OP's request for line2, line3 and line4 to move upwards as well:
Following David Carlisle's suggestion, you can use \raisebox to move the image downwards.
You can then smash the image, which makes LaTeX think the image has no height. This trick means that the image could overlap the bottom of the table, but that won't be a problem if you have enough text in the other two columns.
Result:

Code:
\documentclass[demo]{article}[12pt]
\usepackage{graphicx} % This is already loaded by the atlasnote class
% Just use it to include your plots!
\begin{document}
abc
\begin{table}[h!]
\begin{center}
\begin{tabular}{|c|l|c|}
\hline
ABCD, put me at the top &\smash{\raisebox{-\height}{\includegraphics[height=2.5cm]{invariant_mass_eX_Asymmetric}}} &line1, i wish to be much more at the top\\
& &line2, idem\\
& &line3, idem\\
& &line4, idem\\
\hline
\end{tabular}
\end{center}
\end{table}
def
\end{document}
valign=c. – Werner May 07 '13 at 14:06line2is in the following row of the table so of course it comes below. perhaps you want to make the last columnp{3cm}instead ofcand then putline 1... line2...all in one multi-line entry – David Carlisle May 07 '13 at 14:12