Gimp is second only to Photoshop and, especially since it is free, it might be better. It is great with .jpg files, but I am mot sure it can work with all .eps files. A difficult to learn but very high quality program for .eps and vector graphics based files is Inkscape. Vector graphics rescale better than other graphics.  You can download either or both free from their own home sites on the  Internet. The important thing for drawing images for research articles is not so much the program, but that you, avoid compression and particularly that for files such as .jpg, etc. that you save your images at 300 dots per inch. That makes them very sharp. 

Thanks @Lewis Maccarter