Hi @leena, glad to hear back from you! Lots of posts to answer, so here's a synopsis -

Posting Pictures

Use a photo sharing service like Photobucket or Picasa. Both of those services are free with lots of upload space. Once you upload a photo, it is assigned an IMG link (which looks a lot like an "http://" link). You can then cut & paste that link in any forum thread and the picture will automatically be displayed in your posts. Trying to attach photos using the Pool Forum's vBulletin software is a waste of time. Since this forum runs on a server with limited storage capacity, users just can't be given a lot of storage space or else the forum will crash.

Sand Filters

I am no expert so all I can offer you is this advice - bigger is ALWAYS better when it comes to sand filters. The last thing you want to do is try to run an undersized sand filter with an overpowered pump. Sand filters are describe either by their full sand weight (pounds of sand) or the diameter of the filters "belly" measured in inches. Either way, the bigger the number, the more water flow you get. So your best best bet is to get the largest size sand filter you can reasonably afford. A bigger sand filter always means longer times between cleaning. So if you don't want to backwash a lot, bigger is better.

Pump

Definitely get a 2-speed pump, 1.5HP sounds like it would be more than enough for your pool. The two speed option is desirable because sand filters actually perform better (finer particulate filtration) at lower speeds. So for everyday water circulation you can use the low speed setting and get good energy savings and great filtration. Then, when you need to vacuum or run a robotic cleaner, you can kick it up to high speed for fast vacuuming.

Vendors

Look, Hayward is the biggest name out there. I don't know of anyone who went with Hayward filtration products and hated it. There are other vendors (Pentair, etc) but if you're happy with Hayward, then stick with it.

Sorry I can't be more specific, but I am a DE filter guy so my knowledge on sand filters is limited. You could always call up the Hayward technical support people (I hear they are very helpful) and give them some pool details. They may be able to give you lots of different combinations and options to work with.