If you need a background for your macro and close-up shots of small things, you can make your own. Create them in programs like Photoshop, Photoshop Elements, Paint Shop pro, and similar graphics programs. Design them to fit a standard-sized sheet of paper. Add colors, brush strokes, filters, whatever you like, in the colors you like. Print them out on matte finish paper (the less shine, the better) and store them in archival quality vinyl sleeves. Put them in a notebook for safe keeping.
You can also take pictures to be used as backgrounds - a brick or stone wall, pebbles on a beach, feathery grasses growing in a field, trees, tree bark, rocks, water, aged wood siding, whatever - use your imagination. Print them to fill the page. If you like, you can apply some Gaussian blur to them before printing to give the illusion of shallow depth of field.
Another source for backgrounds can be found on digital scrapbooking sites. Many of those are offered as freebies (for personal use). Crop or resize them to fit to your photo paper and print them out.
The following 3 images were photographed using backgrounds from my original printed collection.
This image was taken with a mirror under the flower and a black foam sheet standing up behind it, so that the part of the mirror that is in the picture reflected only the black foam (and the flower). Natural light was used.
The background for this image is a sheet of cork tile.