From Stormie:
Easel Painting: Although I haven't always been able to do it, I like offering easel painting every day as a free choice activity.  A good way to keep it interesting is to focus on the "shape" and "colors" of the month.  For example, throughout September, if a "Circle" is your main "shape" focus, provide a steady supply of large circles (cut from manilla paper) that are to be used just for easel painting.  If "red, blue, and yellow" are your colors, you might begin with just one color paint, then add another later in the month.  (I like using two primary colors at a time so children can create secondary colors from them.)  By the end of the month, you might have all three colors out as choices.

Easel Preparation: I like covering my easel on Monday in order to save myself extra work that following Friday: I wrap newspaper around the area where children will be painting, holding it in place with masking tape.  I also line the trays with newspapers, and place newspaper under the easel to protect the floor.  On Friday, I simply strip away all the dirty newspaper.  I've also used plastic shower curtains (cut to size) to cover the easel and floor.  They are more attractive and you can just toss them in your laundry at the end of the week.  Yogurt containers are great for putting paints in.  They fit into the easel tray just right, they have a lid so you can cover them each day, and if you have lots of them, throw the used ones away on Friday.  When I haven't had a sink, I like to keep a small bucket of soapy water and towel near the easel.

Paint Preparation: Accidental paint stains will come out of clothing much easier if you place a drop or two of liquid dishsoap into your easel paint containers.

What Do I Mean By Creative Abstract Paintings?
Have children paint a large square or rectangular shaped sheet of paper at the easel.  This way, they can be creatively expressive and the large paper allows them to involve arm movements for making big wide painting strokes.  Once the papers are dry, give the children choices as to what they would like to do with their paintings: Would you like to take it home just like it is, or would you like to take it to the Art Center and work on it some more?  
Going From Abstract To Concrete: I also like to offer a third choice: I like to cut their large paintings into any shape that may fit a theme of the month.  For example, let's say you had put out red paint at the easel with the large sheet of paper.  Later, you could cut large apple shapes from the child's paintings.  You took an abstract painting and turned it into a concrete theme.  The project can now be carried a step further by then allowing the children to work within the theme of "apple" by adding their own collaged stems, leaves, worms, etc.  Or, in October, you could put out orange paint and a large square sheet of paper for abstract paintings, then cut the dry painted papers into pumpkin shapes.  Children could take home their pumpkins as they are or work within the theme and add their own collaged jack-o-lantern faces.  
The important thing is to allow the children to make their own choices.

Zeroes and Ones Easel Painting (a following directions activity): If you plan a special day to focus on numbers 0, 1, and 2, you could instruct the children to do a special easel painting of "zeroes and ones" (this is a fantastic wrist exercise).

Letter/Name Recognition Easel Painting: For each child, tape a stencil of his/her first name initial to the easel.

During your "All About Me" unit, ask children if they would like to paint a picture of themselves at the easel.

Here's a great idea from "Stacie" who says, "I use clear contact paper to cover the surface of my easel -- it's easy to clean, especially if clean-up has to wait until the children leave, and it keeps the surface looking new.

Susan Place, in Jackson, Minnesota uses old plastic tablecloths for the floor in the painting area.

Debbie, in MA says:
Here's what we use to cover our easel: Go to a hardware store (we use Home Depot), and in the paint area, find large rolls of plastic.  Painters use them as drop cloths when they are painting to cover large areas.  Although the rolls are large, the expense is not great, and you can use the amount you originally buy for several years.  This initial expense saves you time and money overall.  The plastic comes in different strengths.  We buy a strong, heavy duty one.  Back in the classroom, we cut it to fit our easel and tape it on.  The plastic is heavy enough to last all year.  At the end of the year we simply strip the plastic from the easel and "voila" a clean-paint free easel.  It has saved us many hours of scrubbing!!  Enjoy!

From Sheryl Bauer: An Extra Special September Easel Activity: 
An Apple for Mommy and Daddy: Provide large red or yellow circle shapes at the easel for children to paint. Once they're dry, have children glue them on an even larger piece of paper.  Then have them spread their fingers apart and make a green handprint at the top of the circle for an apple stem (palm end on the apple).  You could print "A is for Apple" at the top.  If you want to make it a little extra special, children could present it to their parents with this little poem in the center of the apple: